Jawaban:

1.My teacher taught me this formula yesterday, but I ... so I couldn't answer the questions.

A.don't understand

B.didn't understand

C.wasn't understand

D. weren't understand

2.Nina's cat ... sick last week. 

A.is

B.are

C.were

D.was

3.While Erika ... the dinner, my dad got home.

A.were cooking

B.Is cooking

C.cooking

D.was cooking

4.My mom ... at home by 6 o'clock this evening. 

A.had been arriving

B.was arriving

C.had arrived

D.arrived

5.What did you do yesterday?

A.I helped my mom cook fried rice

B.I help my mom cook fried rice

C.I am helping my mom cook fried rice

D.I was help my mom cook fried rice