．The fact has worried many scientists ______ the earth is becoming warmer and warmer these years.

A．what

B．which

C．that

D．though

物体触及掌心，新生儿立即把它紧紧捏住，这是新生儿的（）

A.怀抱反射

B.抓握反射

C.觅食反射

D.吸吮反射