Identify the correct sentence.

a. the fireman ran as quick as he could.

b. fire can silently spread through a house.

c. she held onto the firefighter tight.

d. the fireman climbed direct to the second floor.

The correct option is B.

The other sentences are incorrect because their adverbs lack 'ly'.

For instance, option A ought to be written like this: The fireman ran as quickly as he could. The same applies to the other options.