The speed of the reaction can be increased by keeping the beaker in the sunlight. Thus option B is correct.
The baking soda has been sodium bicarbonate. The reaction between baking soda and calcium chloride results in the formation of calcium carbonate, sodium chloride, carbon dioxide, and water.
To speed up the reaction, the molecules of the reactants have to be speed up in order to attain more collisions between the samples,
The freezing of the sample results in a decrease in the kinetic energy of the reactant molecules. The flat and narrow test tube results in collisions at the normal rate.
However, by keeping the beaker in the sunlight, the light energy has been transferred to the reactants molecule that resulting in an increased collision and speeds up the rate of reaction. Thus option B is correct.
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