2,2-Dimethyl-1,3-propanediol is formed by heating 2-methylpropanal with an excess of formaldehyde and $$\text{Ca(OH)}_2$$. The sequence of reactions taking place in this synthesis is

A

dehydrogenation to 2-methyl-2-propenal followed by addition of formaldehyde

B

dehydrogenation to penta-2,3-diene followed by addition of formaldehyde

C

a crossed aldol reaction followed by a crossed Cannizzaro reaction

D

a crossed Cannizzaro reaction followed by a crossed aldol reaction