1) in the 15th century, leonardo dicaprio wanted to build a helicopter but he couldn't seriously consider doing so because
the technology didn't exist (build ,do) 2. Although H.G. Wells could
imagine travelling to the moon, he failed to understand how it could be done. For
example, he seemed unthinkable it would be possible without special breathing
systems (travel,understand,think) 3. Arthur Clarke enjoys thinking
about space adventures but he avoids writing about things without explaining
how they might be possible one day (think, write,explain) 4. Would you agree to postpone going back to school if you could travel to the moon (postpone, go)