Answer:
They all are made up of cells
The correct option is: CH4 + O2 → CO2 + H2O.
In writing chemical equations, the reactants are usually written to the left of the equation of the reaction while the products are written to the right of the reaction. An arrow pointing in the right direction shows the direction of the reaction. In the question given above, methane and oxygen are the reactants while carbon dioxide and water are the products. The options that states the chemical reaction correctly is option 1.
Nucleus is the right answer i guess

dissolves in water to give

and

ions according to the following reaction:

-------->

+ 2

So, according to the above reaction, 1 mole of

produce 2 moles of

ion,
So, 0.3 mole will give = 0.3 x 2 = 0.6 moles of

ion
So, Molar concentration =

Note: 1L = 1000mL
It would be the controlled variable, which is a baseline to compare your other variables too.
Hope this helps!