_______ the difficulty that he has supporting his big family, he still makes every effort to realize his dream, which I believe is __________ his reach.

A．Despite; within

B．Though; beyond

C．Though; within

D．Despite; of

PWM型晶体管调压器中整形电路的作用是（）

A.将脉冲信号变为连续信号

B.将连续信号变为脉冲信号

C.将梯形波变为矩形波

D.将矩形波变为梯形波