When Tom was a child, he always wondered ________ and asked his mother a lot of questions．
A.how did things work
B.how do things work
C.how things work
D.how things worked
网友回答
D解析因为本句wonder后面跟宾语从句，必须跟肯定句形式，即“how+主语+谓语”，而“how things worked”符合这条规定，所以正确