**The correct answer is option b) 21 **

explaination ::

Let *a* = 2*k* + 1, *b* = 2*l* + 1, *c* = 2*m* + 1

where *k*, *l*, *m are* whole number

*a + b + c* = 13

2*k* + 1 + 2*l* + 1 + 2*z* + 1 = 13

or, *x + y + z* = 5

The number of integrals solutions

\(=^{5+3-1}C_{3-1}=^7C_2\)

\(={7.6\over 1.2}=21\)