Read the following passage carefully and then choose the best answer to  each question.

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-1980, 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 10:00 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.

According to the passage, which of the following is NOT a possible cause of many heart  attacks?

A. decreased blood flow to the heart          

B. increased blood pressure

C. increase in hormones                    

D. lower heart rate

Đột biến được coi là một nhân tố tiến hóa cơ bản vì 

A. đột biến là nguyên liệu quan trọng cho chọn lọc tự nhiên

B. đột biến là nguyên nhân chủ yếu tạo nên tính đa hình về kiểu gen trong quần thể

C. đột biến làm thay đổi tần số tương đối của các alen trong quần thể

D. đột biến có tính phổ biến ở tất cả các loài sinh vật

The activities of the international marketing researcher are frequently much broader than______.

A. that which has the domestic marketer   

B. those of the domestic marketer

C. the domestic marketer does                   

D. the domestic marketer has

Cho các mối quan hệ sau:

(1) Phong lan bám trên cây gỗ.

(2) Vi khuẩn lam và bèo hoa dâu.

(3) Cây nắp ấm và ruồi.

(4) Chim mỏ đỏ và linh dương.

(5) Lươn biển và cá nhỏ.

(6) Cây tầm gửi và cây gỗ.

Có bao nhiêu mối quan hệ được xếp vào kiểu quan hệ hợp tác giữa các loài?

A. 3.

B. 4.

C. 2.

D. 5.