Some researchers are finding that daydreaming may be important to     mental health .Daydreaming ,they say, is      good means of relaxation.

A．the; ／

B．／; the

C．／; ／

D．／; a

基因型为AaBbCcDd和AABbCcDd的向日葵杂交，按自由组合定律，后代中基因为AABBCcdd的个体所占的比例为[ ]

A．1/8

B．1/6

C．1/32

D．1/64