D
If an element doesn’t have a number next to it that means there is only one. There a 4 hydrogens because the number is attached to the hydrogen atom. If there were 4 NH molecules the NH would be in parentheses and the 4 would be outside. Same goes for the oxygen atom and CO3 molecule.
Answer : The correct option is, (D) double replacement reaction
Explanation :
Synthesis reaction : A chemical reaction where multiple substances or reactants combine to form a single product.
It is represented as,

Decomposition reaction : A chemical reaction in which larger reactant decomposes to give two or more than two products.
It is represented as,

Single replacement reaction : A chemical reaction in which the more reactive element replace the less reactive element.
It is represented as,

In this reaction, A is more reactive element and B is less reactive element.
Double replacement reaction : It is a type of chemical reaction where a positive cation and a negative anion of two reactants exchange places to form two new products.
It is represented as,

(X and A are the cations, Y and B are the anions)
The given reaction is:

This reaction is a double displacement reaction.
ca(HCO3)2 this is what i think it is
Answer:

Explanation:
Hello,
In this case, the combustion of methane is shown below:

And has a heat of combustion of −890.8 kJ/mol, for which the burnt moles are:

Whereas is consider the total released heat to the surroundings (negative as it is exiting heat) and the aforementioned heat of combustion. Then, by using the ideal gas equation, we are able to compute the volume at 25 °C (298K) and 745 torr (0.98 atm) that must be measured:

Best regards.
<span>The answer is:
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