A PERT network has three activities on critical path with mean time 3, 8 and 6 and standard deviations 1, 2 and 2 respectively. The probability that the project will be completed in 20 days is

A. 0.50

B. 0.66

C. 0.84

D. 0.95

Please do not use chat terms. Example: avoid using "grt" instead of "great".