问题：
【题文】-This problem is very difficult. -I know,but Jack has working it out.
A．succeed in
B．succeeds in
C．succeeding in
D．succeeded in
【题文】-This problem is very difficult. -I know,but Jack has working it out.
| A．succeed in | B．succeeds in | C．succeeding in | D．succeeded in |
参考答案：