Answer:
CD
Step-by-step explanation:
if B comes after A and you put them together that makes AB so do the same for CD CD is the answer
ANSWER
1001
EXPLANATION
The sum of the first n - natural numbers is

The sum of the first 1000 terms is



The sum of the first 1001 terms is



The difference is

The constant is 3.
This is because when x=1, y=3 and when x=2, y=6 so that is a constant change over each interval as seen in the graph which is 3 :)