In order to understand the reading situation of all the students in the class, Xiao Ming adopted a comprehensive survey method.

(1) 12 people like reading novels, accounting for 30%,

∴The number of students in this class is: 12÷30%=40 (people),

So the answer is: 40;

∴Those who like comics are: 40-4-12-16=8 (people),

As shown in the picture:

(2) In the fan chart, it means that the central angle of the circle for the "Comics" category is 840×360°=72°.

The number of people who like to read "Nutritional and Food" books accounts for all Percentage of class size: 4÷40=10%;

So the answer is: 72, 10%;

(3) Draw a tree diagram to get:

∵***There are 12 equally possible results, and there are 6 situations in which there are exactly 1 boy and 1 girl among the 2 students selected;

∴P (1 boy and 1 girl) =612=12．