Mercury pollution in a local lake can be traced directly to a factory located near the lake's shore. what type of pollution is the mercury ?

a

primary

b

secondary

c

tertiary

What is the next step in muscle contraction after the actin changes shape? (apex)

Which group of algae is characterized by unicellular organisms and includes some members that would be better classified as zooflagellates? euglenophytes red algae sporozoans green algae

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?