Catalyst: Substances which alter  the rate of a chemical reaction and themselves remain chemically and quantitatively unchanged  after the reaction are known as catalysts and the phenomenon is known as catalysis.

If you make a graph of concentration of reactant vs time, the instantaneous reaction rate at a given time is the slope of the tangent line at that point in time. It is also the value of the rate law at a specific concentration (dA/dt is rate = k [A]).

For 2times=10°c.
for 4times=20°c.
for 6times=30°c.
for 8times=40°c.
and for 10times=50°c.

For every 10°C rise of temperature, the rate is doubled. Thus, the temperature coefficient of the reaction = 2

When temperature is increased by 50°, rate becomes =2^(50/10) = 2⁵ times = 32 times

A catalyst is a substance that can be added to a reaction to increase the reaction rate without getting consumed in the process. Catalysts typically speed up a reaction by reducing the activation energy or changing the reaction mechanism. Enzymes are proteins that act as catalysts in biochemical reactions.

For the reaction, A+B⟶C+D, the  variation of the concentration of the products is given by the curve Y.
Initially, the product concentration is 0, then it gradually rises and reaches a maximum value. After that it remains constant. 

This behavior is represented by the curve Y.

The correct answer is option C
The term  in the rate expression refers to the instantaneous rate of the reaction.
It is the ratio of the decrease in the concentration of a reaction to the time taken for this decrease.

The correct answer is Option A.
 
The instantaneous rate is the rate of a reaction at any particular point in time, a period of time that is so short that the concentrations of reactants and products change by a negligible amount.

The correct answer is Option D
The instantaneous rate is the rate of a reaction at any particular point in time, a period of time that is so short that the concentrations of reactants and products change by a negligible amount. The initial rate is the instantaneous rate of reaction as it starts (as the product just begins to form).