1、I spent half an hour（working on）this difficult math problem 括号里为何填working on 而不是to wo

I spent half an hour_______my book. I spent half an hour ___(finish) my homework. I spent half an hour in doing my homework i spent half an month reading the book什么 I spent half an hour swimming 这句话对吗? I spent half an hour on my homework yesterday.（保持原意l ( )half an hour ( )my homework skirt. 英语I spent half an hour getting to the shop.改为同义句：( )( )( )half an hour( )( )to the shop. I spent half an hour getting to the shop改为同义句 I spent half an hour___my homework.Afinish doing Bto finish doing Cfinishing to do Dfinishing doing I spent half an hour on my homework yesterday.（保持原意） I spent half an hour geting to the shop.的同义句 I spent half an hour writing the letter 改为同义句 I spent half an hour finishing ___ work.这里要填the吗?为什么? I spent half an hour arriving at the top of the mountain.同义句 1、I spent half an hour（working on）this difficult math problem 括号里为何填working on 而不是to wo I spent _____ watching TV.A）one and a half hourB）one and half an hourC）one hour and a halgD）a half hour I spent half an hour arriving at the top of the mountain.同义句___ ___ me half an hour ___ ___ to the top of the mountain . I spent half an hour cleaning my room.（同义句转换）It （ ）（ ）half an hour （ ）（ ）my room.