The books of are mayan texts that chronicle mayan life in the 17th and 18th centuries.

I think it is "The books of Chilam Balam are Mayan texts that chronicle Mayans life in the 17th and 18th centuries. 

Right answer: a. comprarías

this question is given using the conditional form. conditional tenses are is used when talking about hypothetical situations and probabilities. also, this is used when making polite requests. so comprarías is the conjugation of the verb comprar that matches the second person singular in the conditional. finally:

¿cuál comprarías tú?

Cancer es una de las enfermedades mas comunes en el munde que no tiene curación. poreso muchos sientificos han intentafo años para curar. cancer se puede crear con radiacion o una mutuacion el una celula. poreso los humanos son mad comunes de tener cancer, por las celulas.