Which of the following can be used to measure absolute time? select all that apply.

varves

tree rings

law of superposition

ratio of c-12 to c-14 in a bone sample

which statements are true? select all that apply.

an atom is the smallest complete part of an element.

an element is a pure substance made of one kind of atom.

the nucleus is the tiny center of an atom, and it contains protons and neutrons.

isotopes are atoms of the same element that contain the same number of neutrons but different numbers of protons.

the time required for one-half of the atoms from a sample of a radioactive substance to decay is called its

half-life

beta decay

alpha decay

isotope number

which statements about radiocarbon dating are true? select all that apply.

it's useful for dating all inorganic things.

it's useful for dating some organic (once-living) things.

it's useful for dating some materials that are millions of years old.

it's useful for dating some materials that are thousands of years old.

for a living organism, which of the following are true? select all that apply.

the ratio of c-14 to c-12 remains constant.

the ratio of c-14 to c-12 increases over time.

the ratio of c-14 to c-12 decreases over time.

the amount of c-14 is less than the amount of c-12.

potassium-40 (k-40) decays into argon-40 (ar-40). after 1.25 billion years, 20 grams of k-40 would be reduced to 10 grams. how much of the original k-40 would remain after 5 billion years?

0 grams

1.25 grams

2.5 grams

5 grams

uranium-238 (u-238) decays into lead-206 (pb-206). which of the following are true statements? select all that apply.

u-238 is the parent, and pb-206 is the daughter.

u-238 is the daughter, and pb-206 is the parent.

a rock sample containing a relatively small amount pb-206 is old.

a rock sample containing a relatively small amount of pb-206 is young.

if a sample is thought to be several million years old, which method would best to determine its absolute age?

c-14/c-12

ar-40/k-40

pb-206/u-238

a fossil bone is tested, and no c-14 is found. what can be said about the fossil's age?

it is 5,730 years old.

it is less than 5,730 years old.

it is more than 5,730 years old.

absolute-age dating techniques can be used to determine the age of which of these? select all that apply.

earth

some rocks

some fossils

substances made entirely of pb-206

substances made entirely of ar-40