Carrie sends five text messages to her brother each Saturday and five text messages to her brother each Sunday. Carrie sends two text messages to her brother on each of the other days of the week. Over the course of four full weeks, how many text messages does Carrie send to her brother?
(A) 15
(B) 28
(C) 60
(D) 80
(E) 100
Each week, Carrie sends 5 messages to her brother on each of 2 days, for a total of 10 messages. Each week, Carrie sends 2 messages to her brother on each of the remaining 5 days, for a total of 10 messages.

Therefore, Carrie sends $10+10=20$ messages per week.

In four weeks, Carrie sends $4 \cdot 20=80$ messages.

ANSWER: (D)