—Alice, you look puzzled. Have you understood it?

—Yes, I         another problem just now.

A. have thought of      B. am thinking of

C. had thought of       D. was thinking of

―Alice, you look puzzled. Have you understood it?

―Yes, I          another problem just now.

       A．have thought of    B．thought of           C．was thinking of    D．had thought of

—Alice, you look puzzled. Have you understood it?

—Yes, I          another problem just now.

A．have thought of           B．thought of           C．was thinking of             D．had thought of

 —Alice, you look puzzled. Have you understood it?

—Yes, I         another problem just now.

A. have thought of      B. am thinking of

C. had thought of       D. was thinking of

—Alice, you look puzzled. Have you understood it?

—Yes, I 　　　　another problem just now.

A. have thought of　　 B. am thinking of

C. had thought of　　　 D. was thinking of

—Alice, you look puzzled. Have you understood it?

—Yes, I 　　　　another problem just now.

A. have thought of　　 B. am thinking of

C. had thought of　　　 D. was thinking of

---Alice, you look puzzled, Have you understood it?
---Yes．I _____another problem just now．

---Alice, you look puzzled, Have you understood it?

---Yes．I _____another problem just now．

---Alice, you look puzzled, Have you understood it?
---Yes．I _____another problem just now．

1. A.
   l have thought of
2. B.
   am thinking of
3. C.
   had thought of
4. D.
   was thinking of