How many chromosomes are in a human kidney cell?

What is thought to have caused the mass extinction at the end of the cretaceous period?

Which food could be transported in a galvanized metal container?

What do isotopes of uranium have the same number of? what do they have a different number of? a) same number of protons; different number of electrons b) same number of protons; different number of neutrons c) same number of electrons; different number of protons d) same number of neutrons; different number of protons