父母常为他做生日蛋糕 Parents ( ) or his birthday 括号里该填什么?

问题描述:

父母常为他做生日蛋糕 Parents ( ) or his birthday 括号里该填什么?

usually make him a cake

父母常为他做生日蛋糕.
Parents ( ) on his birthday.
应填:
always make birthday cake for him