34) B
The statement in the question suggests a correlation between trade union members and less financial returns for a degree.
Since we have the correlation, we need a cause for this link.
A – Wrong
Trade union membership is irrelevant
B – Correct
Since trade union members are graduates in low paying jobs, there is less financial return for a degree.
C – Wrong
This statement talks about people without degrees whist trade union members do have degrees.
D – Wrong
Age is irrelevant.
E – Wrong
Again, the number of trade union members is not a cause for the correlation.