Despite their______of interest, Fleming kept trying to develop chemical     ______ it would be safe and effective.

A．lack, so as to

B．lacking, so as to

C．lack, so that

D．lacking, so that

保健按摩的特点是（）。

A、消除疲劳

B、健身防病

C、简便易行，无损伤无副作用、效果显著

D、延缓衰老