Analyzing angle relationships of triangles

which statements are always true regarding the diagram? check all that apply.
a) m∠3 + m∠4 = 180°
b) m∠2 + m∠4 + m∠6 = 180°
c) m∠2 + m∠4 = m∠5
d) m∠1 + m∠2 = 90°
e) m∠4 + m∠6 = m∠2
f) m∠2 + m∠6 = m∠5