Answer:
2 or ii
Step-by-step explanation:
ANSWER

EXPLANATION
If ABCD is a parallelogram, then
line AB is parallel to line DC .
This means that,

and

are alternating angles.
Alternate angles are congruent.
This implies that,

We group like terms to obtain,

This simplifies to,

Also, if ABCD is a parallelogram then,
BC is parallel to AD. This means that,

We group like terms to get,

This simplifies to,

We divide both side by 4 to get,
I believe the right answer is B!
Option B i.e. Non-Euclidean
∡b is a vertical angle to ∡a and therefore a twin, and we know that ∡a = 120°, thus since ∡b = ∡a, ∡b = 120° as well.
a full circle has a total of 360°, ∡d and ∡c are vertical angles, namely two angles across from each other at a junction, and therefore ∡d = ∡c.
∡a + ∡b is 120° + 120° thus 240°, since a circle has a total of 360°, 360 - 240 = 120, so the other two angles pick up that slack and divide it among each other evenly, 120/2 = 60, so ∡d = ∡c = 60°.