Articles are sometimes omitted in recipes and other instructions that are meant to be followed while they are being read. Such omissions are inappropriate, however, in nearly all other forms of writing, whether formal or informal.
It is not always necessary to repeat articles with paired items.
However, if one of the items requires a and the other requires an, both articles must be included.
Exercises:
Needed words 1
Needed words 2
Needed words 3
Needed words 4