The correct demonstrative adjective for this sentences would be "este".
* Este niño en la foto es mi primo Francisco". Because "ESTE" refers to a singular male subject. If it would have been a girl, the correct option would have been "ESTA". For plurals we need to use "estos" and "esa" when it is a singular, female and we point the subject at a certain distance. "Esa es mi prima" --> That is my cousin (over there)
The singular form of los libros is el libro. The reason why we use el is because libro is masculine.
D because cero is 0 which already cancels 2 then diecinueve is 19
Oct 31st to nov 2nd ............