Answer:
Step-by-step explanation:
It dangles, and neither a nor b fix the problem.
a
doesn't because your your eyes are doing the laughing. This is less wrong than b
b)
Same problem with b, this time the tears are doing the laughing.
The way to fix the problem is not to use something that uses a comma before the subject. A worse example is Running up a tree, I saw a squirrel. You mean the squirrel, I hope. I don't run up trees. Never have.
So the way to fix the sentence is
I laughed until tears filled my eyes.