1. B. responsibility (take responsibility for st: có trách nhiệm với cái gì)

2. C. The (The only + N: ... duy nhất)

3. C. suitable (adj): phù hợp 

Question 1. You are old enough to take …….. for what you have done.

A. responsible

B. responsibility

C. responsibly

D. irresponsible

`=>` B. responsibility

Vì công thức (take responsibility for st:

dịch : có trách nhiệm với cái gì)

Question 2. John is ………… only child in his family so his parents love him a lot.

A. a

B. an

C. the

D. no article

`=>` C. the

Vì công thức The (The only + N: ... 

dịch :  duy nhất) 

Question 3. According to the boss, John is the most …… for the position of executive secretary.

A. supportive

B. caring

C. suitable

D. comfortable

`=>`C. suitable

Vì công thức (adj)

dịch : phù hợp