Explanation : The major shortcoming of waterfall model is the difficulty in accommodating changes after requirement analysis. System testing, maintenance of system and accommodating changes after feasibility analysisare minor shortcoming. For more information on waterfall model Refer:Software Engineering | Classical Waterfall Model. Option (A) is correct.
Explanation : For a program of k variables boundary value analysis yields 4 * k + 1 test Robustness testing yields 6 * k + 1 worst case testing yields 5 * k. So, option (C) is correct.