1. What is the meaning of Avogadro's number? A. number of grams per one mole of a substance

B. simplest whole-number ratio of a chemical formula

C. whole number ratio that is a multiple of a chemical formula

D. set number of particles in one mole of a substance

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

(b) which contains higher levels of vitamin b, oranges or spinach?

explanation:

you can eliminate a, c, and d because they are questions based on opinions.