http://i64.tinypic.com/3321j09.jpg - Question 3.. why is the answer (b) and not (d)..?

3.
The equation for the reaction between methanol and butanoic acid :
CH₃OH + C₃H₇CO₂H → C₃H₇CO₂CH₃ + H₂O

Obviously, the formula of the ester formed is C₃H₇CO₂CH₃, but not C₃H₇CO₂C₂H₅.

Alternatively, CH₃OH and C₃H₇CO₂H totally contains 5 carbon atoms, so that the ester should also contain 5 carbon atoms, i.e. C₃H₇CO₂CH₃.

...... The answer is: D. C₃H₇CO₂CH₃ (not B.)

because it is upside down