Evidence of a powerful volcano, which erupted under the ice sheet of West Antarctica around 325BC and might still be active now, __________ so far by British scientists.
She changed so much that I could hardly _______ her when we met again after a separation of 20 years.
—When did you go to the United States? -- I remember _______ there when I was ten.
I prefer studying English at home ______the match.
We can’t use the machine now, for it _______.
To her surprise, the life she had been looking forward to ________ to be unpleasant.