4.  －Could I ask you a rather personal question?

－________.

A. Yes, don’t worry                      B. Of course, go ahead

C. Yes, help yourself                     D. Of course, why not

3. He ______ on the bed_____ to his parents that blackbirds had_____ their eggs on Mars.

A. lay; lying; lied                        B. lied; lied; lied 

C. laid; laid; laid                       D lying; lied; laid

2. Children’s curiosity may _____________ many useful inventions.

A. lead to           B. take place      C. gather in         D. bring away

1. ―I want to know if I        smoke here.

―No, you       .Could you see the sign “NO SMOKING” there?

A. can; needn’t             B. must; can’t        C. shall; won’t              D. may; mustn’t

S_n最大,最大值为S₈₄=2108.4------------------------------10分

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当n取接近于的自然数时,即n=84时,

方法二:S_n=50n+=-0.3(n-)²+-------------------8分

所以(S_n)max=S₈₄=50×84+=2108.4----------------------10分

方法一:因为d=-0.6<0, a₁=50>0, a₈₄>0 a₈₅<0 --------------------------8分

∴n>  ∵n∈N^*---------------------------------5分

∴当n≥85时, a_n<0

即从第85项开始以后各项都有a_n<0  ------------------------------6分

(2)(满分4分)