Which model shows two equal expressions when a = 4?
A. a + 1 + 1 + 1 + 1 = 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1
B. a + a + a + a = 1
C. a + a + a + a = 1 + 1 + 1 + 1
D. a + a = 1 + 1 + 1 + 1 + 1 + 1