Question

Their coming without notice really                    our difficulties.

A．added

B．added up

C．was added to

D．added to

Answer 1

D

add可以作为及物动词，构成“add...to”，表示“把……加到……上”；也可以用作不及物动词，构成短语 add to...，表示“增添，添加”； add up to则表示“共计”。