OK, let's solve the other three.

98. Add diagonally i.e.;
10+16+14=40
11+16+(13)=40 so, 13 is the correct answer which is option A.

99. Add row-wise i.e.;
17+16+17=50
20+15+15=50
25+17+(8)=50 so, 8 is the correct answer which is option C.

100. Add diagonally i.e.;
7+12+17=36
15+12+(9)=36 so, 9 is the correct answer which is option C.