A. true
b. ​false, the probability that a or b will occur is upper p left parenthesis upper a or upper b right parenthesis equals upper p left parenthesis upper a right parenthesis plus upper p left parenthesis upper b right parenthesis minus upper p left parenthesis upper a and upper b right parenthesisp(a or b)=p(a)+p(b)−p(a and b).
c. ​false, the probability that a or b will occur is upper p left parenthesis upper a or upper b right parenthesis equals upper p left parenthesis upper a right parenthesis times upper p left parenthesis upper b right parenthesisp(a or b)=p(a)•p(b).
d. ​false, the probability that a or b will occur is upper p left parenthesis upper a or upper b right parenthesis equals upper p left parenthesis upper a right parenthesis plus upper p left parenthesis upper b right parenthesisp(a or b)=p(a)+p(b).