Blisters containing clear fluid, less than 1cm in diameter is:

 # Blisters containing clear fluid, less than 1cm in diameter is: 

A. Vesicle 

B. Bulla 

C. Pustule 

D. Nodule 

The correct answer is A. Vesicle.

Vesicles: These are small blisters containing clear fluid that are less than 1 cm in diameter.

Bullae: These are elevated blisters containing clear fluid that are greater than 1 cm in diameter.

Pustules: These are blisters containing purulent material and appear yellow.

Nodules: These lesions are present within the deep mucosa. The lesions may also protrude above the mucosa forming a characteristic dome‐shaped structure. A good example of an oral mucosal nodule is the irritation fibroma.

Ref:  Burket's Oral Medicine, 13th Edition.