Explain why

a. Black box testing cannot usually test all aspects of the specifications.
b. Glass box testing cannot usually test all execution paths through the code. (This does not mean that glass box testing cannot visit all lines and visit all branches of the code.)

a. There are too many things to test. For example, if the specification involves integers, we cannot test for all possible integers
b. There are too many paths. For example, if there are N two-way branches, there are 2N paths.