Which best describes how to add 9.73 and 21.6?
a. align the digits on the left digit.
add from left to right, regrouping as necessary.
b. align the digits on the right digit.
add from right to left, regrouping as necessary.
c. align the digits on the decimal point.
add from left to right, regrouping as necessary.
d. align the digits on the decimal point.
add from right to left, regrouping as necessary.