An event or thing that occurs once in every three months is called Quarterly.
There are four quarters in a year.

The table above shows the four quarters of a year.
A. July
B. August
C. September
D. December
Correct Answer: A
Step 1: Bob visits his grandparents once in a quarter year.
Step 2: Quarter of a year equals three months.
Step 3: As Bob visited them in the month of April, his next visit would be after three months.
Step 4: Three months after April comes the month of July.
Step 5: So, Bob's next visit to his grandparents' would be in the month of July.
Q1: If an event happens quarterly and it last occurred in April, when will it happen next?
Q2: How many months make up the 3rd quarter of the year?
Q: How many months are there in a quarter?
A: There are three months in a quarter.
Q: How many quarters are in a year?
A: There are four quarters in a year.