Whenaspacecrafttravels,oneofthemajorproblemsisreentryintotheEarth’s_______.
Itisnot---_______formetoreturnallthebookstothelibrarynowbecauseIstillneedsomeofthemformyresearch.
Inordertoincreaseouroutput,weneedtoimportmoreproduction_______.
Whentravelingaloneinthemountains,you’dbettertakea_______withyouincaseyougetlost.