D. Cả ba câu đều đúng

Vì gỗ và nhựa đều là chất cách điện tốt, vừa cách được mặt đất, vừa tránh được điện giật  

câu cuối tell chuyển thành told bạn nhé

1,My mother bought a nice gift for me last week.

2,Last month i sent a gift to my pen pal.

3,Why did you go to the dentist yesterday?

4,Eating vegetables is good for you.

5,My uncle cut my hair and it looks different now.

6,The nurse measured me and tell me to get on the scales.

\(n_{CH_4}\)\(=\dfrac{11,2}{22,4}=0,5\left(mol\right)\)

\(CH_4+2O_2\xrightarrow[]{t^o}CO_2+2H_2O\)

 \(0,5\)        \(1\)                               \(\left(mol\right)\)

\(V_{O_2}=1.22,4=22,4\left(l\right)\)

\(V_{kk}=22,4:\dfrac{1}{5}=112\left(l\right)\)

In the modern world, people can easily communicate with telephone, radio, and computer.

with → by 

Giải thích:

+To communicate with + N (cá nhân/tập thể cụ thể) (giao tiếp trực tiếp)  

+To communicate by + N (sự vật - vô tri vô giác) (giao tiếp bằng,qua vật dụng nào đó)

1,Mr John never allows his daughter to swim in the river with her friends.

2,My application for the job was turned down.

Gọi số cần tìm là \(\dfrac{ }{ab}\) (điều kiện bạn tự viết nhé)

Vì tổng 2 chữ số là 10 nên ta có:

    \(a+b=10\)     (1)

⇔\(b=10-a\)

Vì tích 2 chữ số nhỏ hơn số đã cho 12 nên:

    \(a.b+12=10a+b\)     (2)

Thay (1) vào (2) ta được:

    \(a\left(10-a\right)+12=10a+10-a\)

⇔\(10a-a^2+12=9a+10\)

⇔\(-a^2+a+2=0\)

⇔\(\left(a+1\right)\left(2-a\right)=0\)

⇔\(\left[{}\begin{matrix}a+1=0\\2-a=0\end{matrix}\right.\)

⇔\(\left[{}\begin{matrix}a=-1\\a=2\end{matrix}\right.\)

Mà \(a\in N,a\ne0\)

⇒\(a=2\)

⇒\(b=10-a=10-2=8\)

Vậy số cần tìm là 28

 You may think that everybody knows how to make friends, but for some people it isn't so easy. (71)……… they want to be friends with others, they always seem to be alone. Sadly, some of them get depressed (72)……… this. We wanted to find out how these people can make friends, (73)……… we asked a group of 14-year-olds what sort of people they prefer. The most important thing, they said, is that they can get (74)……… with them. They like to be friends with kind and generous people, who rarely get angry (75)……… others. They also like people who laugh at their jokes, and can tell (76) ……… stories, too. They (77) ……… be interested in what the group does, and perhaps even think of (78) ……… new things to do. We also asked the group how not to make friends with them. Here are some of the things they mention: always telling others what they (79)……… to do, telling lies about people, and talking about themselves (80)……… the time!

71. A. Although     B. Even                  C. Despite              D. However

72. A. for               B. about                 C. of                       D. under

73. A. since            B. because              C. so                       D. as

74. A. on                B. down                 C. back                   D. in

75. A. to                 B. against               C. with                   D. by

76. A. amused        B. cheerful             C. smiling              D. funny

77. A. can               B. ought                 C. need                   D. should

78. A. annoying     B. exciting           C. embarrassing     D. disappointing

79. A. have             B. could                 C. may                   D. must

80. A. most            B. all                      C. every                 D. only

Gọi \(\left\{{}\begin{matrix}n_{CuO}=x\\n_{PbO}=y\end{matrix}\right.\left(x,y>0\right)\)

n\(_{CO}\)= 0,84 : 28 = 0,03 (mol)

CuO + CO \(\xrightarrow[]{t^0}\) Cu + CO\(_2\)

   x        x          x        x   (mol)

PbO + CO \(\xrightarrow[]{t^0}\) Pb + CO\(_2\)

   y        y          y        y   (mol)

Theo bài ra ta có hệ phương trình:\(\left\{{}\begin{matrix}80x+223y=3,83\\x+y=0,03\end{matrix}\right.\)

                                                    ⇔\(\left\{{}\begin{matrix}x=0,02\left(mol\right)\\y=0,01\left(mol\right)\end{matrix}\right.\)

a)%CuO = \(\dfrac{80.0,02}{3,83}.100\%\)= 41,78%

   %PbO = 100% - 41,78% = 58,22%

b)\(n_{CO_2}\)= x + y = 0,02 + 0,01 = 0,03 (mol)

   \(V_{CO_2}\)= 0,03 . 22,4 = 0,672 (l)

c)

CO\(_2\) + Ca(OH)\(_2\) → CaCO\(_3\) + H\(_2\)O

0,03                          0,03             (mol)

\(m_{kt}\)= 0,03 . 100 = 3 (g)

(x² - 5x)² + 10(x² - 5x) + 24 = 0

<=> (x² - 5x)² + 10(x² - 5x) + 25 - 1 = 0

<=> (x² - 5x + 5)² - 1 = 0

<=> (x² - 5x + 4)(x² - 5x + 6) = 0

<=> (x - 1)(x - 4)(x - 2)(x - 3) = 0

<=> x - 1 = 0 hoặc x - 4 = 0 hoặc x - 2 = 0 hoặc x - 3 = 0

<=> x = 1 hoặc x = 4 hoặc x = 2 hoặc x = 3

Vậy \(x\in\left\{1;2;3;4\right\}\)là nghiệm phương trình