Thomastik-Infeld 137 Dominant Nylon Core Viola String, Medium Gauge, 4/4 Scale, D

Posting says strings, but i read in comment below it is only one string. nowhere does it state just one string, let alone which string! ?

Will this fit a 16”viola?

Are these strings ball or loop end?

Is this a set? I feel silly for asking but the price is what caught my eye