词汇运用，根据句意，写出括号内所给单词的适当形式：
His poor memory is really a ________(advantage)to him．
Sometimes, it is very difficult to make correct ________(decide)．
动词填空
Before our teacher reminded us, we ________(send)the e-mails．
He promised us that she ________(tell)him about the event at the proper time, but actually(事实上)she didn't．
Fifty students have entered the writing competition since it ________(hold)for the first time．
Boys and girls, please read the guidebook carefully, or you ________(get)lost during the visit．
It is said that he devoted much of his time to ________(write)his new novel．
－It seems that you know a lot about the story．
－Well．We ________(read)it many times．
All the rules must ________(explain)to the players clearly before the game starts．
You had better ________(not laugh)at others because everybody makes mistakes．