Fill the following blanks with correct forms. 用所给单词的正确形式填空。
He                   （have）breakfast at 7:30 yesterday morning. 
I                               (sleep) when she knocked at the door.
They                          (play) the guitar from 2 p.m. to 4 p.m. yesterday afternoon.
Jack                         (make) modal planes while I was reading.

【参考答案】

(1)
was having (2)
was sleeping (3)
were playing (4)
was making