Take a look at the item again:
As Alex squeezed down the narrow row of chairs.
(A) His heavy book bag
bumped the large soda perched on a desk,
(B) sending a shower of diet
cola into Teresa's lap, (C)
soaking her jeans.
You wanted to do this:
As Alex squeezed down the narrow row of chairs. His heavy book bag bumped
the large soda perched on a desk, sending a shower of diet cola into Teresa's
lap soaking her jeans.
Removing the comma after lap is an error. Soaking her jeans is a participle phrase. You will often use a comma to connect a participle phrase to the end of a sentence.
You might want to review the rules.
Go back to the sentence to try again.