An index fossil is a fossil that is useful for dating and correlating the strata in which it is found.
Or it is a fossil that helps you find the date where it has been found. I rephrased that.
Answer:
The correct answer is b polar covalent
Explanation:
When two atoms joined by covalent bond has difference in their electronegativities at that time polarity arise.
When the electronegativity difference is low such as 1.3 then the polar bond formed by the two atoms are called polar covalent bond.For example H2O
on the other hand polar bond formed by two atoms having high difference in their electronegativities is called ionic bond.For example NaCl.
The answer is A. the solar ultraviolet ray breaks the molecule apart
Control group: 50 dogs continuing their normal diet
Experiments group: 50 dogs chosen to eat the new food
Independent variable: dog food
Dependent variable: the dogs’ weight