Which of the following is not a type of epithelial cell

The three principal shapes associated with epithelial cells are—squamous, cuboidal and columnar. Squamous epithelium has cells that are wider than their height (flat and scale-like).

but where is the options?

"do a testcross with a homozygous recessive plant."

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.