Answer:
A communicable disease
Explanation:
Diseases that can be transferred are known as communicable diseases.
The answer is A i think if it’s wrong someone correct me
Answer:
The element will be 
Explanation:
Given that,
Number of proton = 80
Number of neutron = 81
Number of electron = 79
We know that,
The atomic number is equal to the number of proton.
So, the atomic number is 80.
According to atomic number,
The element will be mercury.
We need to calculate the atomic mass
Using formula of atomic mass

Put the value into the formula


We need to find the element
Using atomic mass and atomic number


So, the element will be

Put the value of A and Z
Hence, The element will be 
Bromide gives away 1 electron (valency of 1) and Ca wants to gain 2 electrons (valency of 2) therefore 2 Br ions are needed