Answer;
-An influenza virus particle
Step-by-step explanation;
-An influenza virus particle is bigger in size compared to a ragweed pollen grain. Influenza virus particles have a size of 80–120 nm. However, the length of each particle varies considerably, owing to the fact that influenza is pleomorphic, and can be in excess of many tens of micrometers, producing filamentous virions.
-On the other hand, researchers found that ragweed pollen grains release SPPs in the size range of 0.5–4.5 μm, small enough to reach lower airways.