I _______ in London for many years, but I’ve never regretted my final decision to move back to China.
| A．lived | B．was living |
| C．have lived | D．had lived |
Carl Linnaeus made great contributions to ________ plant species.
| A．group | B．have grouped | C．grouping | D．been grouping |
He observed a stranger _______ around the store at 12 p.m. last night.
| A．to hang | B．hang | C．hanging | D．to be hanging |
Once ______ , the plan can’t be changed.
| A．begin | B．beginning | C．began | D．begun |
They asked me so many ______ questions that I got ______.
| A．confusing; confusing | B．confused; confusing |
| C．confused; confused | D．confusing; confused |
.Jumping out of ______ airplane at ten thousand feet is quit ____ exciting experience.
| A．\; the | B．\;an | C．an; an | D．the; the |