Marcus put the 3 red apples and 3 green apples he just bought in the same bag and then selects an apple from the bag without looking. The probability of picking a red apple is __________.

A.  1/2; picking a red apple is just as likely as picking a green apple

B.  1/2; picking a red apple is less likely than picking a green apple

C.  1/3; picking a red apple is less likely than picking a green apple

D.  1/3; picking a red apple is just as likely as picking a green apple