1.help sb.do(to do) sth.
2.be busy doing sth.
3.go on doing sth.(on是介词,介词后面动词用ing时态)
5.like to do sth.
6.从句中语序应该是陈述句语序,所以是it cost
7.同6
补充:因为句子的意思是爱迪生自己建立了一个科学实验室,所以填himself.根据句子的意思判断填词,也是一种方法.
1.help sb.do(to do) sth.
2.be busy doing sth.
3.go on doing sth.(on是介词,介词后面动词用ing时态)
5.like to do sth.
6.从句中语序应该是陈述句语序,所以是it cost
7.同6
补充:因为句子的意思是爱迪生自己建立了一个科学实验室,所以填himself.根据句子的意思判断填词,也是一种方法.