answer :- (c) 65
reason-
Given : TLB access time = 10 ns
main memory access time = 50 ns
TLB hit ratio= 90% i.e (0.9)
now we first need to find miss ratio that is [1- TLB hit ratio]
miss ratio= 1- 0.9= 0.1
now calculating the effective access time by formula,
hit ratio X (TLB access time + memory access time) + miss ratio X (TLB access ratio + 2 X memory access ratio)
= 0.9X(10 ns + 50 ns)+ 0.1 X (10 ns + (2 X 50 ns))
=0.9 X 60 ns + 0.1 X 110ns
=54 ns + 11 ns
=65 ns