Choose the word from the drop-down menu that completes each sentence. A/An star system is made of two stars. A/An star system is made of no more than a few thousand stars. A/An star system is made of more than a million stars. the answer in order is :
Binary
open cluster
globular cluster

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

Which type of bond is found between the atoms of a molecule? a. metallic b. delocalized electron c. covalent d. ionic

Because air contracts as it cools, the air pressure inside a freezer is typically lower than on the outside. why do ice cubes inside a freezer tend to shrink over time? a. the ice dissolves oxygen from the air, forming a denser crystalline matrix. b. the ice reacts chemically with carbon dioxide in the air, forming gaseous carbon compounds. c. the ice melts, and then the liquid freezes as ice crystals on the bottom of the freezer. d. the ice sublimes, and then the water vapor deposits as ice crystals on the sides of the freezer.