Crop failures is my best educated guess. I hope this helps
Tu is used when you referring to someone you already know, someone in an informal or even fellow classmate, so it's false but you are supposed to greet someone by using "usted".
Tenochtitlan was built on Lake Texcoco
E, because E is the only option that corresponds to actions you would use when making a sandwhich
High school escuela secundaria
