The table below shows the amounts of lemon juice and sugar used in each container of lemonade. The ratio of lemon juice to sugar is 1:r, where r is the unit rate. Use the table to determine r.
Lemon Juice (cup) Sugar (cup)
1/2 1
2 4
3 6
A. 2
B. 1/2
C.1
D. 2/3