D is true because NO2 is a catalyst, and a catalyst is a compound which makes a reaction occur faster (not necessarily more effectively, creating more product, but it decreases the amount of time it takes).
Isotopes of the same element differ only in the number of neutrons an atom has. Its still the same element because the number of protons define an element. Just their neutrons and mass number is different.
Answer:
12.01
Explanation:
(12.00*98.93% + 13*1.07%) /100% = 12.01
I think A. Molecules interact without bonds breaking
