Answer:
The slopes of OA, OB ans OC are integer values.
Explanation:
If a line passing through two points then the slope of the line is

If one point is origin then the slope of the line is

The slope of line OA is

It is an integer.
The slope of line OB is

It is an integer.
The slope of line OC is

It is an integer.
The slope of line OD is

It is not an integer.
The slope of line OE is

It is not an integer.
The slope of line OF is

It is not an integer.
Therefore the slopes of OA, OB ans OC are integer values.