Correct Answer - A::C
P(exactly one of M,N occurs)
`P{(MnnbarN)uu(barMnnN)}=P(MnnbarN)+P(barMnnN)`
`=P(M)-P(MnnN)+P(N)-P(MnnN)`
`=P(M)+P(N)-2P(MnnN)`
Also, P(exactly one of them occurs)
`={1-P(barMnnbarN)}{1-P(barMuubarN)}`
`=P(barMuubarN)-P(barMnnbarN)=P(barM)+P(barN)-2P(barMnnbarN)`
Hence, (a) and (c ) are correct answers.