In a DNA duplex with four base-pairs, how many of each of the following chemical groups are there

Are answers correct, and can I get help with part B

a. strands- Two
b. deoxyribose sugars----not sure
c. phosphate groups-Six
d. 5' ends-Two
e. purines-Four
f. pyrimidines-Four

Nicely done, all answers are correct. As for B, you identified that there are 2 strands of DNA and there are 4 base pairs. Each DNA base pair would consist of 2 nucleotides, so 4 base pairs with 2 nucleotides each would mean there are 8 nucleotides in this DNA duplex. Each nucleotide consists of a single deoxyribose, so there would be 8 deoxyribose sugars.

Hope this helps