15. another name for the interstellar matter that will eventually form a star is a. supernova b. red giant c. black hole d. nebular 16. in the milky way, the most abundant gas in emission nebulae is a. helium b. hydrogen c. argon d. nitrogen 17. massive star terminate in a brilliant explosion called a a. red giant b. protostar c. neutron star d. supernova 18. all stars, regardless of size, eventually a. turn into black dwarfs b. explode c. run out of fuel and collapse d. become black holes 19. the sun is a a. black hole b. black dwarf c. main-sequence star d. red giant

Select the correct answer from each drop-down menu. during the day, plants produce by splitting water molecules in the light-dependent reactions of photosynthesis. at the same time, plants use cellular respiration to produce some of the needed by the light-independent reactions to make sugars. during the night, plants produce because takes place.

Refer to this portion of a dichotomous key for fish identification to answer the question. 1. (a) has a single dorsal fin ® 5 (b) has a double dorsal fin ® 2 2. (a) one fin is spiny, the other is smooth ® 3 (b) one fin is not spiny or smooth ® 4 5. (a) has small fin on back near tail ® 6 (b) has no fin on back near tail ® 7 6. (a) has barbs near the mouth ® catfish (b) does not have barbs near the mouth ® 10 7. (a) tail is asymmetrical ® 8 (b) tail is symmetrical ® 9 10. (a) scales are small ® trout (b) scales are large ® whitefish what is the next step to complete to identify a fish that has a single dorsal fin, no fin on the back near the tail, and no barbs near the mouth? step 2 step 5 step 7 step 10

Abird flies by moving its wings up and down. which two systems are most directly responsible for the movement of a bird's wings? a. skeletal and muscular systems b. respiratory and muscular systems c. skeletal and digestive systems d. respiratory and digestive systems