The correct options are
A Number of ways in which committee can be formed, is 10C2×20C3
B Number of ways in which a particular professor is included, is 9C1×20C3
C Number of ways in which a particular lecturer is included, is
10C2×19C2
D Number of ways in which a particular lecturer is excluded, is
10C2×19C3
Number of ways of selecting 2 professors out of 10 and 3 lecturers out of 20 is 10C2×20C3
Number of ways when a particular professor is included, is
10−1C1×20C3=9C1×20C3
Number of ways when particular lecturer is included, is 10C2×19C2
Number of ways when a particular lecturer is excluded, is
10C2×20−1C3=10C2×19C3