The price of the bus ticket is much ____ than before.

A．cheap

B．cheapest

C．cheaper

D．the cheapest

（1） A与2x²y-5xy²+6y³的和为3x²-4x²y+5y²，求A．

（2）已知：（2a+2b+1）（2a+2b-1）=63，求a+b的值．

（3）若2x+y=3，求4^x•2^y的值．