“We showed it’s possible for animals to live in an environment they are not used to: microgravity,” Poynter says.

In 2014, Poynter and Maccallum achieved another first. They led the engineering team that helped former Google exec Alan Eustace skydive from the edge of the stratosphere. That’s when it hit them: The balloon-parachute system they designed for Eustace could be transformed for tourism and research. So they formed World View, with MacCallum serving as chief technical officer.

What does the pronoun “it” in paragraph 5 refer to?

A．The system designed for Eustace can be used for more purposes.

B．Poynter and Maccallum hope to achieve more firsts in their career.

C．Poynter and Maccallum have helped Alan Eustace to skydive.

D．Maccallum will serve as a chief technical officer in World View.