The complementary mRNA strand is AGCUACCU.
We must adhere to the base pairing guidelines:
In DNA, adenine (A) pairs with thymine (T), but in RNA, it pairs with uracil (U).
Adenine (A) and thymine (T) couple together.
Guanine (G) and cytosine (C) pair together, and vice versa.
The complementary mRNA strand for the DNA strand TCGATGGA would therefore be created by substituting uracil (U) for thymine (T):
DNA: T C G A T G G A
RNA: A G C U A C C U
So, the complementary mRNA strand is AGCUACCU.