Carbon has a significant role in the chemistry of living organisms because it tends to form four bonds with other atoms. Which best explains the ability of carbon to form these bonds? A. 6 total protons B. 4 valence electrons C. 6 total electrons D. 4 valence protons

Significant figures are digits read directly from the measuring instrument plus one more digit, which is __ by the observer.

Mike and mitchell decide to have a foot race. they mark off a stretch of 100 yards, and recruit cindy to work the stopwatch. after running the race and looking at the results, cindy declared that mitchell was the fastest. so how did the boys times compare?

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.