After swimming for hours he was tired what is the personal pronoun in the sentence below

Which type of irb review does not require an irb approval but does require a determination by the irb or an irb designee?

Atrajectory has an initial velocity of 1,000 meters per second, and 5 seconds later, it has a velocity of 500 meters per second. which is the acceleration of the trajectory?

Is an example of a nation that uses a democratic republic type of government.