B: eighth
The eighth note gets the beat because the bottom number of the key signature is an 8.
The bottom number of the key signature resembles which note gets the beat, while the top number resembles how many beats per measure.
Examples: 3/2: half note gets beat; 4/4 = quarter note gets beat; 9/8: eighth note gets beat; 12/16 sixteenth note gets beat, and so on and so forth.