The phrase "a prefers" is not correct in standard written English.
It is typically used incorrectly as it lacks a subject that would make it grammatically sound.
Example: "A prefers to stay home rather than go out."
Alternatives: "A favors" or "A chooses".
For example, Researcher A prefers textual educational resources, written in Portuguese or Spanish, with difficulty degree of post-graduate courses.
(Suppose an agent A prefers X to Y, Y to Z and Z to X, and that A will pay some small amount of money $P to exchange Y for X, Z for Y, and X for Z.
This CLiPS study indicated that Staphopain A prefers a Leucine residue for the P2 site of the substrate, corresponding with the Leucine at position 34 in CXCR2.
We identified LLD↓A as the Staphopain A cleavage site in CXCR2, a finding that largely corresponds with a recent study using CLiPS showing that Staphopain A prefers a Leucine at the P2 substrate subsite.
So this individual A prefers four to three, three to two, and two to one, but we can't say that he prefers or she prefers four to three more than she prefers three to two.
Roommate A prefers to study at the library.
