He tried his best to solve the problem, _______difficult it was.
A. however B. no matter
C. whatever D although
There is only one more day to go your favorite music group play live.
| A．since | B．until | C．when | D．before |
Brian is gifted in writing music; he is very likely to be Beethoven.
| A．a | B．an | C．the | D．不填 |
More expressways in Sichuan soon to promote the local economy.
| A．are being built | B．will be built |
| C．have been built | D．had been built |
The books on the desk, covers are shiny, are prizes for us.
| A．which | B．what | C．whose | D．that |
You _____be careful with the camera. It costs!
| A．must | B．may | C．can | D．will |