The correct answer would be C, vacuole.
Answer:
Activation Energy is the Energy that Must be Overcome/reached by Reactants for Products to be formed.
I'd go with the 2nd Option.
Answer:

Explanation:
Empirical formula of ionic compound formed by two ions
and
is
(for
) of AB (for x = y)
The above empirical formula is in accordance with charge neutrality principle
Here each cation (
and
) can form two ionic compounds by combining with two given anions (
and
).
So the four ionic compounds are: 
13 An Ionic Bond
these are the characteristics of an ionic bond compounds like NaCl have these characteristics
14 substances could be compounds or elements hence not all substances are compounds
15 It is not water. The chemical composition of water is H2O not H202
(H202 is hydrogen peroxide and is toxic)
1) All matter is made of atoms. 2) Atoms are indivisible and indestructible.