Fact 1: Some mollusks are nearly microscopic.

Fact 2: Mollusks are abundant fossils.

Given the two facts above, answer the question "what are sometimes nearly microscopic?" with the following options: 
- peachleaf willow
 - major threat to health
 - elephants
 - abundant fossils
 - Veins and arteries.
 - trees
 - barnacles
 - weathering


 

    abundant fossils     