What is the name of the solid substance being produced from the chemical reaction between the two clear solutions?

Correct Precipitate.

When two clear aqueous solutions react, the insoluble compound formed as a product is termed as precipitate. The formation of an insoluble precipitate is considered as one of the evidence that the reaction has taken place. Such reactions in which clear solutions react to form insoluble precipitates are called precipitation reactions. These reactions come under double replacement reaction.

Example as a precipitation reaction is,

AgCl is the white colored precipitate formed in the above reaction

the answer is option a.