40
(A)Afterward
(B)Beforehand
(C)Occasionally
(D)Periodically

(A)Afterward(adv) We had a swim and afterward we lay on the beach for a while
(B)Beforehand(adv) -earlier (than a particular time)
I knew she was coming that afternoon because she had phoned beforehand to say so.
我知道她那個下午要來訪，因為她在來訪前有打電話來告知。
(C)Occasionally(adv) -sometimes but not often
(D)Periodically(adv) -in a way that is repeated after a particular period of time
Period有月經的意思，periodcally就是週期性的意思

(A)Afterward 之後
(B)Beforehand 遇先
(C)Occasionally 偶爾
(D)Periodically 定期

He secretly asked the most popular kids in an elementary school to make errors in the morning gym exercises. 

 40 , he asked the class if anyone had noticed any mistakes during gym period時期.

(A)afterwards翻譯：過後，以後，後來。
(B)beforehand翻譯：事先，預先。
(C)occasionally翻譯：偶爾，間或；有時。 
(D)periodically翻譯：週期性地，定期地。