According to the adsorption theory of catalysis, the speed of reaction increases because

• Correct answer
  A

  adsorption lowers the activation enegry of the reaction
• B

  the concentration of reactant molecules at the active centres of the catalyst becomes high due to adsorption
• C

  in the process of adsorption, the activation energy of the molecules becomes large
• D

  adsorption produces heat which increases the speed of the reaction

Hence, the correct answer is option: 'A'.