Which component is required for the activation of some enzymes?

a) presence of a co-factor
b) basic ph levels in the substrate
c) higher enzyme concentration
d) lower temperature in the substrate

The correct answer is option A.

Presence of a co-factor is required for the activation of some enzymes. Co-factors are generally metal ions or small molecules (non-protein).Co-factors helps enzymes bind substrate tightly.  For example, NAD⁺/NADH is a co-factor which is required for the activation of the enzyme dehydrogenase. NAD⁺ is the oxidized form and NADH is the reduced form.

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.