DDT蓄积性很强，它属于以下哪类物质？（）

A．异氰酸甲酯

B．一氧化碳

C．硫化氢

D．有机磷农药

E．有机氯农药

Directions: Write a letter to your cousin, who is going to take the college entrance examination and feels stressed, giving her some suggestions. Write your letter with no less than 100 words. Do not sign your name at the end of the letter. Use“Li Ming”instead. Do not write the address.