I guess few folks here missed out on a critical piece of linkage.
Post Grads in
Engg and Science from Oly Uni get great jobs. Many grads (Read as anywhere from 1% to 100%) out of ALL Grads (read as Engg, Science, Business, Biology, etc) of Plateau College went to Oly Uni later on for post grad.
Conclusion: If you go to Plateau College as an undergrad, you have good chances of getting jobs.
Logical jump: Plateau College (any degree) -> Good jobs
Assumptions: (Backtracking) Good jobs <- Oly Uni post grad in engg and science <- Plateau College (engg and science undergrad)
If you look at the logical jump in the conclusion and the assumptions, you will notice that it is not necessary for any undergrad to go to OLy Uni. For example, if X is business major in Plateau, he/she need not go to Oly Uni. This means that the author cannot conclude that it is wise for X to join Plateau since they will get a good job.
So to make the argument's conclusion airtight, B is the best strengthener.
Hope that helps!