Answer No 1:
A concentration gradient can be described as a phenomenon by which molecules travels from an area which is highly concentrated to an area which has low concentrations of that molecule.
Answer No 2:
A molecule is said to be diffusing down a concentration gradient when molecule acquire the phenomenon of concentration gradient i.e move from higher concentration to lower concentration. This mechanism is also termed as passive transport. Active transport is the opposite of passive transport. In active transport, molecules move against the concentration gradient i.e from an area of lower concentration to an area of higher concentration.
It is between A and B.
But if the species is going to be extinct, that means that they are being threatened.
So the answer is B.
A molecule is made of more than one atom of differing elements that can be simplified while an element cannot be simplified because it is only one atom of one type of element.
