Right now, a new team of engineers _______________ a motor that runs entirely on hydrogen., is designing, was designing, Before the internet became famous, scientists ______________ private networks to share data for years., have been using , had been using, Nikola Tesla _____________ on wireless energy transmission when he ran out of funding., has been working, was working , Since the 1960s, NASA ____________ the possibilities of deep space travel., has been exploring, is exploring , By the time the light bulb was patented, Edison ________________ with different materials for a long time., had been experimenting, is experimenting.

Continuous Tenses

by
Print
Embed

Leaderboard

Visual style

Options

Switch template

)
Continue editing: ?