In the figure above, if 11 perp12 and 13 / 14,. Which of the following statements must be true? I.a+b=90 II. a + c = 90 III. b=dA. I onlyB. II onlyC. I and II onlyD. II and III only

From the given figure
Since l3 // l4, then
a = d ----- corresponding angle
b = c ----- corresponding angles
Since l1 is perpendicular to l2, then
In the small triangle
a + b = 180 - 90
a + b = 90 degrees
In the big triangle
d + c = 180 - 90
d + c = 90 degrees
Let us look at the correct statements
I. a + b = 90 is correct
II. a + c = 90
Since b = c
Then replace b by c in I, then
a + c = 90 is correct
III. b = d is false
Then the correct statements are I and II
The answer is C