Law on obligations and contracts: Under article 1207 and 1208

Task/Question: On March 1, 2020, X, Y and Z executed a promissory note binding themselves to pay Php.90,000.00 to A, B and C. the promissory note is now due and demandable.

A) Can A, B and C ask payment to X alone for the entire Php. 90,000.00? Why?

B) Can "A" alone demand payment against X, Y and Z for the payment of the entire Php.90,000.00? Why?

C) Assuming that "A" demand payment to "X" alone, how much can "A" collect from "X"? Why?

D) In the situation given, what is the obligation, joint or solidary? Why?