Illustrative Cases:

1. "D" borrowed Php10,000.00 from "C" on September 1, 2021. He executed a promissory note promising to pay the indebtedness on October 5, 2021. Upon the arrival of the designated date for payment, is demand necessary in order for "D" to incur delay?

2. Taxi driver D, driving recklessly, killed pedestrian X and his passenger P. What are the sources of obligation of D and that of his employer to P and X?

3. S sold B a specific car for P20,000.00 payable in four equal installments:

January 1, 2021 - P5,000.00

February 1, 2021 - 5,000.00

March 1, 2021 - 5,000.00

April 1, 2021 - 5,000.00

B paid the first installment but failed to pay the remaining installments. What is the effect if S receives the installment for the month of April amounting to P5,000.00, without reservation as to the installments due on February and March?