— Why didn't you come for the game last Sunday?
— My father asked me _______ my sister at home.
A:babysit
B:babysitting
C:babysat
D:to babysit
古人云:“久居芝兰之室,不闻其香”,这是由于大脑的____适应的缘故。
北方地区的水果主要有( )
人们通常用钨这种金属制造电灯的灯丝,是因为钨的____高。