It’s joe mama mamamamamammamamama ammamamamammama
D, 2Cu + O2 → 2CuO. A is wrong because oxygen is a diatomic element, meaning it always has to come in the form of O2 in the case of gas. B is wrong because the equation isn't balanced correctly; there's two oxygens on the reactants side, while only one oxygen on the products side. C is wrong because it's saying you're STARTING OUT with CuO already: that doesn't correspond with the word problem. Thus leaves D, where the equation is balanced correctly, has the diatomic oxygen, and ends with CuO.
The molar concentration of the original HF solution : 0.342 M
Further explanation
Given
31.2 ml of 0.200 M NaOH
18.2 ml of HF
Required
The molar concentration of HF
Solution
Titration formula
M₁V₁n₁=M₂V₂n₂
n=acid/base valence (amount of H⁺/OH⁻, for NaOH and HF n =1)
Titrant = NaOH(1)
Titrate = HF(2)
Input the value :

Answer:
Waters' boiling point decreases with increases in elevation because of the atmospheric pressure.
For example, the higher in elevation you are. The lower the atmospheric pressure is. In other words heated water reached boiling point quicker.
B is true since evaporation changes a liquid into a gas and dondensation turns a gas into a liquid