Which of the Following Best Categorizes Sites (A)and (B)in the Aldehyde

Which of the following best categorizes sites (a) and (b) in the aldehyde shown below?

A) (a) and (b) are both nucleophilic sites.
B) (a) and (b) are both electrophilic sites.
C) (a) is a nucleophilic site,and (b) is an electrophilic site.
D) (a) is an electrophilic site,and (b) is a nucleophilic site.