<span>A.H2O = water, so it is a liquid at room temperatures (melting point = 0C) and melting point must be below 20C
B.HCl = A gas at room temperatures, so melting point (-114C) is definitely lower than 20C.
Melting points of the aqueous solution (solution in water) at different concentrations are all below that of water, i.e. 0C.
C.CH4 = A gas at room temperatures, so melting point (-182C) must be below 20C.
D.MgCl2 = A white powdery solid at room temperatures, so its melting point (714C) must be above 20C (So this is the only one among the four choices that melts above 20 ° C).</span>
<span>C</span>⁰<span> H</span>₃⁺¹<span> C</span>⁰<span> O</span>⁻²<span> O</span>⁻²<span> H</span>⁺¹
C is 0
H = + 1
O = - 2
B, the height above or below sea level
I believe it is sand. <span />
