Which of these are true about triangulation?

a. The greatest possible distance between the two triangulation observations from the surface of the earth is earth's diameter.
b. we can measure distances to many other stars using triangulation from earth.
c. if we lived on mars, we would be able to measure bigger distances using triangulations. Assume the smallest paralax that can be measured is 0.02" for both mars and earth.
d. all of the statements are true.