If there's a lot of work ----- ,I'm happy to just keep on un

填加 to be done 到空格是不对的.只能填:A to do
因为不定式作定语时,当与被修饰的词形成动宾关系时,则用不定式的主动式表被动意思.
a lot of work 与 to do 形成动宾关系,即:to do a lot of work ( work是to do的宾语)
类似的句子有:I have much homework to do now ,so I can't go out with you .
Do you have anything to drink