单词拼写。根据下列句子及所给汉语注释，写出空缺处各单词的正确形式。

1. He looked at her with a ______ (混合) of amusement and depress.

2. ______ (明显), I'll have to think about your offer carefully.

3. Could you ______ (递送) this letter to the teachers' office?

4. Old people are more ______ (可能) to suffer back problems.

5. As they ______ (接近) the wood, a rabbit ran out of the trees.

拼缝间隙一般不得超过2mm，个别间隙达到3mm，其焊缝长度不超过50㎜，总的数量应小于焊缝总长的（）。

A、15%

B、20%

C、25%

D、30%