The correct answer is C: 0.83. If a person is chosen at random in the survey, P(regular or plain)=0.83.
Regular=A and Plain=B
P(A and B)=0.27
P(A or B)= P(A)+P(B)-P(A and B)
P(A or B)= (0.27+0.19+0.32)+(0.27+0.05)-0.27
P(A or B)= 0.78+0.32-0.27
P(A or B)= 0.83
Therefore, P(regular or plain)=0.83.
Therefore, the correct option is C: 0.83.