Answer is b)External fragmentation
Since segmentation follows Variable Partition technique (Memory is divided into unequal size partitions)
let us say there are three processes which require 50KB,30KB,50KB
Initially there is 140KB memory is available with the OS now OS duty is to allocate the memory to processes
140 KB is divided into variable size partitions
since it is Variable partiotion technique OS uses BEST FIT algorithm to allocate the memories to the processes
P1 wants 50KB so best among all the partitions is 70 KB so p1 will be allocated to that slot now P2 wants 30 KB as direct partition of 30KB is available P2 will be alloted there
now the diagram looks like this
Now one more request P3 with 50 KB came but we couldn't able to allocate them even though we have 40+20=60KB free memory
this is external fragmentation.
If suppose we have partitions like
OS can combine these free Blocks and it can make it as new partition of 60KB and it can allocate it .so occuring of External fragmentation depends on the patitions made by OS initially(if it makes 30KB,60KB,40KB respectively then we will not come across problem of External fragmentation for this problem) so Segmentation MAY suffer from External fragmentation