帮我填下:请用所给动词的适当时态填空
1 This is the third time that I ____(visit) the Science Museum.
2 At present many scientists ____(make)a study of living things in the ocean.
3--Is there anything wrong?
--No, So far I___(have) no trouble.
4 Don't worry. Your son___(come)back in a minute .
5 The Marathon Race____(become) one of the most popular sport events for ordinary people in the past few years.
不一定要全帮我解决,能解决几题是几题,谢拉