Irrelevant. To weaken this argument, we would need to know that Redville has many more library users than Glenwood. This just tells us that Redville currently has more library users who walk to the library — but this is exactly what we would expect based on the second premise, since the library is located in Redville. Even if this were true, Glenwood could have many more library users, who currently have to drive or take the bus to the library. So this doesn't weaken the argument.

This significantly weakens the argument. Notice that this choice even answers the potential objection that having a library in Glenwood will turn some Glenwood residents who currently aren't library users into library users. Even if the library is in Glenwood, and so within walking distance for residents of central Glenwood, the number of library users in Glenwood is less than the number of Redville residents currently using the library. This weakens the claim that moving the library to Glenwood would put it "within walking distance of a larger number of library users."

This doesn't weaken the argument. It doesn't strengthen it either, though it may seem to: maybe the number of people using the library is increasing already because more Redville residents are becoming dedicated library users, and would still go to the library even if it were moved to Glenwood. What we need to know is whether Glenwood has more library users among its residents than Redville. This answer choice doesn't tell us that.

This might seem like it weakens the argument, since the people who currently drive or take public transport to the library probably include some Glenwood residents. But for one thing, we don't know how many library users commute from outside either Redville or Glenwood. It could also still be true that the library, if moved to Glenwood, would be "within walking distance" for Glenwood residents even if many of them chose to drive or take public transport there anyway.

This doesn't weaken. This just gives us information about "most" library users overall. We need to know how many library users live in central Glenwood versus central Redville.