Ensure proper base pairing in an mRNA strand with the following sequence: CAGAUGUACGGACGAUAA. Check all options below to confirm correct pairing, making the necessary substitutions (T for U and U for T) and ensuring A pairs with U and C pairs with G:

a.Substitute the letter T for the letter U.
b.Substitute the letter U for the letter T.
c.Ensure that A matches U and C matches G.