It was not rare in ______that 
people in ______fifties went to university for further education.
| A．1980s; their | B．the 1980s; the | C．the 1980s; their | D．1980s; the |
I went along the beach thinking of nothing ____.
| A．in brief | B．in doubt | C．in harmony | D．in particular |
The dangerous virus ____ in the next few weeks in the laboratory can cause fatal diseases.
| A．studying | B．studied | C．to study | D．to be studied |
All the dishes in this menu, unless ____ stated, will serve two to three people.
| A．aside | B．otherwise | C．meantime | D．or |
Edward, you play so well, but I _____ you play the piano.
| A．didn’t know | B．hadn’t known | C．don’t know | D．haven’t known |
She’ll never forget her stay there ______ she found her son who had gone missing two years before.
| A．that | B．which | C．where | D．when |