Which of the following statements is true?

a. A piece of magnesium is made only of magnesium atoms.
b. All 118 elements occur naturally on Earth.
c. Protons and neutrons orbit the nucleus of an atom.(i picked this one and it was wrong)
d. Electrons are found in the nucleus.

Where is the following?

27. =3,500,000 x 4,000 = 14,000,000,000

Muscle fiber i think that i right

Answer is: value of q is 5·10⁻⁶m.chemical reaction: mg²⁺(aq) + co₃²⁻(aq) → mgco₃(s).c(mg²⁺) = 2.5·10⁻³ m; concentration of magnesium cations.c(co₃²⁻) = 2.00·10⁻³ m; concentration of carbonate anions.q = c(mg²⁺)  · c(co₃²⁻).q = 2.5·10⁻³ m  · 2.00·10⁻³ m.q = 5·10⁻⁶m.q = 0.000005 m.