In the electrolytic method of obtaining aluminium from purified bauxite, cryolite is added to the charge because it reduces the melting point of Bauxite (from 1200^oC to 800^o−900^oC) and also it increases the electrical conductivity of the mixture.

Hence the correct option is (B).

The most common form of seed dormancy is endogenous physiological dormancy. It is the type of dormancy that is relieved by periods of moist chilling stratification. In nature, seeds get their necessary moist chilling in the ground over the winter. This synchronizes germination in the spring. We can mimic this effect by placing seeds in a moist environment in the refrigerator.

Hence, the correct option is (D).

The mechanism that Darwin proposed for evolution is natural selection. Because resources are limited in nature, organisms with heritable traits that favour survival & reproduction will tend to leave more offsprings than their peers , causing the traits to increase in frequency over generations. Thus, the survival of the fittest. 

Hence, the correct option is (D).

E = αt + 1/ 2 βt², 

The above equation is in the standard form of the parabola. According to this, the graph will be a parabola, such that first emf increases and then decreases.

The graph between E and t:

Reflex ovulation is, ovulation occurring shortly after brief exposure to a sensory stimulus.

Ovulation in rabbits occurs only when copulation (= coitus) begins. Obviously, it is a reflex reaction to coitus. That's why, female rabbits are called 'reflex ovulators'.

Hence, the correct option is (A).

As given, the temperature is increased from T₁ to T₂, then new constants become k₃ and k₄ respectively. 

Rate constant increases with increase in temperature. 

So, k₁ < k₃ and k₂<k₄.

Hence, the correct option is (B).