The problem was so complicated that Mr. Smith had to______his brains.A．crackB．checkC．rackD

The problem was so serious that the general manager had to take______ himself to solve it.

What was the problem with the original mobile？A．It was made of aluminum.B．It wasn"t large

What he said was so complicated that I _________ after the first couple ofsentences.

At the meeting there was a hot argument and so many problems were left______.A．to solveB．s

Everyone was tired, so Bill got up and made a motion that the remaining problems ______unt

The complicated problem can be solved by the computer within__________ a few seconds