Answer:
Covalent is the type of bond.
Answer:
The number of electrons in the outermost shell of an atom determines its reactivity. Noble gases have low reactivity because they have full electron shells. Halogens are highly reactive because they readily gain an electron to fill their outermost shell.
Explanation:
Answer: B. It is an ether because it is unable to to form a hydrogen bond, so it is less soluble than water
Explanation: Alcohols 
are more soluble in water as they can form hydrogen bonding with water whereas ethers 
are less soluble as they do not form hydrogen bonds with water.
For formation of hydrogen bond, the electronegative atom (F, Oand N) must be attached to hydrogen and in ethers (ROR), there is no hydrogen directly attached to electronegative oxygen atom, thus are less soluble in water.
I believe the answer is B. Definitely not D or A, and C doesn't makes sense.
First, let us define Electronegativity. Electronegativity is "the ability of an atom to attract electrons." In addition, electronegativity increases in elements from left to right, while on the other hand, electronegativity decreases from top to bottom in an element group. It decreases because the atomic radius increases as we go downward an element in the group.
