Question

2. My sister and my brother18 years old. *A. `m notB. isn'tC. aren't​

Answer 1

Ответ:

aren't. Потому-что my sister and my brother это множественное число

Answer 2

My sister and my brother aren’t 18 years old

Во множественном числе 3 лица — are; aren’t. В нашем случае — aren’t

Answer 3

The correct option is:

C. aren't

So the sentence should be: "My sister and my brother aren't 18 years old."