Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 55 to 64.

Although most universities in the United States are on a semester system, which offers classes in the fall and spring, some schools observe a quarter system comprised of fall, winter, spring, and summer quarters. The academic year, September to June, is divided into three quarters of eleven weeks each beginning in September, January, and March: the summer quarter, June to August, is composed of shorter sessions of vary length.

There are several advantages and disadvantages to the quarter system. On the plus side, students who wish to complete their degrees in less than the customary four years may take advantage of the opportunity to study year round by enrolling in all four quarters. In addition, although most students begin their programs in the fall quarter, they may enter at the beginning of any other quarters. Finally, since the physical facilities are kept in operation year round, the resources are used effectively to serve the greatest number of students. But there are several disadvantages as well. Many faculty complain that eleven-week term is simply not enough for them to cover the material required by most college coursed. Students also find it difficult to complete the assignments in such a short period of time.

In order to combine the advantages of the quarter system with those of the semester system some colleges and universities have instituted a three-term trimester system. In fourteen weeks, faculty and students have more time to cover material and finish course requirements, but the additional term provides options for admission during the year and accelerates the degree programs for those students who wish to graduate early

Which of the following would be the best title for this passage?

A. The Semester System

B. The Academic Year

C. Universities in the  United States

D. The Quarter System

Ta có :

\(P=\dfrac{14-x}{4-x}=\dfrac{4-x+10}{4-x}=1+\dfrac{10}{4-x}\)

Để P nhận giá trị nguyên => 10 chia hết cho 4-x

=> 4-x\(\in\) Ư(10)={±1;±2;±5;±10}

Ta có bảng :

tự lập bảng nha

Thực hiện phép lai ở gà: Gà mái lông đen với gà trống lông xám thu được 100% F₁ lông xám . Cho F₁ tạp giao được F₂ có tỉ lệ kiểu hình 25% gà mái lông xám: 25% gà mái lông đen : 50 % gà trông lông xám. Cho biết tính trạng màu lông do 1 cặp gen quy định. Trong các kết luận nào sau đây, có bao nhiêu kết luận đúng?

(1) Chỉ có ở gà mái lông xám mới biểu hiện hoàn toàn

(2) Tính trạng lông xám trội hoàn toàn so với lông đen

(3) Gen quy định tính trạng màu lông trên NST giới tính

(4) Gà trống F₂ có 2 kiểu gen

(5) Cho các gà trống F₂ giao phối với gà mái lông xám theo lý thuyết đời con cho kiểu lông đen 25%

A. 3

B. 0

C. 2.

D. 1.

phải

2/5 là đơn thức có bậc là 0

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 30 to 34.

As heart disease continues to be the number-one killer in the United States, researchers have become increasingly interested in identifying the potential risk factors that trigger heart attacks. High-fat diets and „life in the fast lane” have long been known to contribute to the high incidence of heart failure. But according to new studies, the list of risk factors may be significantly longer and quite surprising.

Heart failure, for example appears to have seasonal and temporal patterns. A higher percentage of heart attacks occur in cold weather, and more people experience heart failure on Monday than on any other day of the week. In addition, people are more susceptible to heart attacks in the first few hours after waking. Cardiologists first observed this morning phenomenon in the mid-1980s and have since discovered a number of possible causes. An early-morning rise in blood pressure, heart rate, and concentration of heart-stimulating hormones, plus a reduction of blood flow to the heart, may all contribute to the higher incidence of heart attacks between the hours of 8:00 A.M and 10 A.M.

In other studies, both birthdays and bachelorhood have been implicated as risk factors. Statistics reveal that heart attack rates increase significantly for both females and males in the few days immediately preceding and following their birthdays. And unmarried men are more at risk for heart attacks than their married counterparts. Though stress is thought to be linked in some way to all of the aforementioned risk factors, intense research continues in the hope of further comprehending why and how heart failure is triggered.

What does the passage mainly discuss?

A. cardiology in the 1980s

B. risk factors in heart attacks

C. diet and stress as factors in heart attacks

D. seasonal and temporal patterns of heart attacks

Số phân tử ADN trong một tế bào sinh tinh của ruồi giấm ở kì sau của giảm phân I là

A. 4

B. 2

C. 8

D. 16

Điểm giống nhau giữa các hiện tượng: di truyền độc lập, hoán vị gen và tương tác gen là: 

A.Các gen phân li độc lập, tổ hợp tự do  

B.Tạo ra các biến dị tổ hợp 

C.Thế hệ F1 luôn tạo ra 4 kiểu giao tử tỉ lệ bằng nhau  

D.tạo ra thế hệ con lai ở F2 có 4 kiểu hình