The writer suggests that when talking to others, the speaker should .

• A、know that listeners will show him that they understand his words

• B、express himself clearly even when he sees signs of understanding

• C、notice listener’s signs of understanding

• D、look directly into his listener’s eyes

What’s the reason for twins to be at a disadvantage in their intellectual development?

• A、They can only understand their own private language

• B、They communicate with outsiders less than non-twins.

• C、There is little stimulation for them.

• D、Adults don’t like to talk with them.

60（）