The northern cardinal, a nonmigratory songbird, was rare in Nova Scotia in 1980; the province was considered to be be...

Jacob on November 14, 2018

Answer A gives us an alternative reason for the conclusion in the argument, and thus weakens the logical connection.

That is: the conclusion of this argument is that warmer winters are probably responsible for the northern cardinal’s proliferation. But answer A gives an alternative explanation for why cardinals have proliferated since 1980 — far more common bird feeders, which are an important source of nutrition to wintering birds. This weakens the argument that it must have been the warmer winters.

I hope that helps!