Jumping out of _______ train running at a speed of 200 kilometers per hour is quite _____ dangerous practice.
| A．/; the | B．/; a | C．a; a | D．the; the |
He is always full of ______ as though he never knew tiredness.
| A．strength | B．energy | C．force | D．power |
Apples are usually sold by ______weight, and eggs are sometimes sold by ______ dozen.
| A．the; the | B．不填; a | C．不填; the | D．the; a |
Susan, ______ university student from Europe, teaches me ______ art in her spare time.
| A．an; 不填 | B．a; the | C．a; 不填 | D．an; the |
These young people are now making an active ______ to beautify our city.
| A．part | B．effort | C．decision | D．plan |
--- My son is lost. Did you see a boy pass by here?
--- I saw ______ boy hidden behind ______ tree over there. You may go and have a look.
| A．a; the | B．不填；the | C．a; 不填 | D．a; a |