Which sentence is correct? It's hard to tell what their going to do.
It's hard to tell what they're going to do.
It's hard to tell what there going to do.

It's hard to tell what they're going to do.

Explanation:

they're= they are

1- cleans/ tidies up

2- were

3-would be

4- had known

5-takes

6-must be/ have to be/should be

either a donut or a sphere or a pancake or a flat sphere. it depends on where the vertical line is.

if the line goes through the center of the circle and is perpendicular to a diameter containing the center, then you get a flat circle.

if the line and the diameter of a the circle meet in the center of the diameter and at an angle, you get a pancake.

if the line is on the circumference of the circle and is at right angles   to the circle you get a ring.

if the line contains the diameter, you get a sphere.

the the line is parallel to the diameter and touches the circumference, you get a donut.