What is the main purpose of presidential primaries and caucuses?

In general, primaries use secret ballots for voting. Caucuses are local gatherings of voters who vote at the end of the meeting for a particular candidate. The candidates then campaign across the country to explain their views and plans to voters. They may also participate in debates with candidates from other parties.

Explanation:

hi, according to my research the answer to the first question would be false. al tabari was the author of the first medical encyclopedia & he was a persian scholar not arab