The cell parts does not work alone. The cell consists of many organelles specialised for a particular function to keep the entire cell entity functioning efficiently and effectively. For example, the mitochondria produces ATP to power cellular processes such as glycolysis and the nucleus stores genetic information safely for protein production.
According to the information given, the missing mRNA sequence strand is the 4th from the given option which is AUG AAA CGU CCU. As the complementary of A in RNA is U, G is C and for T is A.