What happens next in this paragraph?

How to count in binary
Learn what binary means.
Our normal counting system is called decimal, or " base ten. " we have ten different symbols for writing numbers, ranging from 0 to 9.
Pick from:
[A]. Multiply and divide to get that number. Subtract from that number to get pi.
[B]. The base ten symbols are : Columns. These can be used to represent labels, so for example, in " 3 " row per quart of jar, there are nine columns.
[C]. If this is your first time counting binary numbers, you'll feel that you're going too low and you'll try another method. Flashcards: you can use flashcards to write binary numbers in numeric order from 0 to 9.
[D]. Binary is a " base two " system, using only the symbols 0 and 1. Add one by changing the last 0 into a 1.
[D].