Computer Network Gate 2005 IT closed

Question

In a communication network, a packet of length L bits takes link L1 with a probability of p₁or link L2 with a probability of p₂. Link L1 and L2 have bit error probability of b₁ and b₂respectively. The probability that the packet will be received without error via either L1 or L2 is

A) (1-b1)Lp1+(1-b2)Lp2

B) [1 - (b1 + b2)L]p1p2

C) (1 - b1)L (1 - b2)Lp1p2

D) 1 - (b1Lp1 + b2Lp2)