The correct options are
A Same reactants may give different products by using different catalysts.
B A catalyst does not change ΔH of a reaction.
Same reactants may give different products by using different catalysts as different catalysts have different specific functions to mould the reaction towards a specific product.
A Catalyst does not change the △H of a reaction as △H is the difference between the enthaply of reactants and products.
Catalysts are required in very small amounts to catalyse the reaction.
The catalytic activity of a solid catalyst depends upon the strength of chemisorption.
From the above statements, we can see that options (a) and (b) are correct.