Tail-Feather Length in Birds Is Sometimes a Sexually Dimorphic Trait

Multiple Choice

Tail-feather length in birds is sometimes a sexually dimorphic trait. That is, the trait differs substantially for males and for females. Researchers studied the relationship between tail-feather length (measuring the R1 central tail feather) and weight in a sample of 20 male and 21 female long-tailed finches raised in an aviary.
The linear correlation coefficient (r) between weight and tail-feather length in male long-tailed finches is 0.46. Approximately what percent of variation in tail-feather length can be explained by weight among male long-tailed finches?

A) 21%
B) 46%
C) 68%
D) 92%