¿son isósceles todos los triángulos equiláteros?

technically yes, but all the sides are equal, so they are their own type of triangle. you kinda answered your question. no, they aren't, they are equilateral.

Yes

Step-by-step explanation:

SPANISH: Un triángulo es isósceles cuando tiene dos lados iguales; esto no descarta que los tres lados sean iguales, de modo que todo triángulo equilátero sea isósceles, pero no se cumple el enunciado recíproco.

ENGLISH: A triangle is isosceles when it has two equal sides; This does not rule out that the three sides are equal, so that all equilateral triangle is isosceles, but the reciprocal statement is not fulfilled.

Lo siento si mi español está mal, solo he comenzado a aprender :)

answer: the answer is d