Asset allocators intended...
It's actually "Asset allocators create..."
The problem with B is that you're not sure what which
is referring to: mutual funds or portfolios. Same problem with C: what is intended
qualifying? Mutual funds or portfolios?
Typically, intention is associated with a person or a process. It's reasonable to assume that, in this case, the asset allocators (= asset manager) have intentions.
Simplify as follows:
Asset allocators create portfolios with the intention to produce good results in ....
Compare with a similar structure:
Asset allocators create portfolios with the motivation to produce good results in ....
A appears to be the best answer.