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.
Answer:
Let, X be the oxidation state of Cr in K
2
Cr
2
O
7
.
2(+1)+2X+7(−2)=0
2+2X−14=0
2X=12
X=+6
Hence, the oxidation state of Cr in K
2
Cr
2
O
7
is +6.
Metal is shiny, has a high electrical conductivity, a high thermal conductivity, and has a high density. Hope this helps.
Umm well its particles are always moving and excited so they are not so close
Answer:
for the first it is B i do not know for the second
Explanation:
i took the quiz hope this helped