Which of the following acids lose $\mathrm{CO}{}_2$ readily on simple warming to about 100-150 ${}^{\circ }$C?

Only acids with a carbonyl group beta to the carboxyl group decarboxylate easily by the cyclic transition state: 3-oxobutanoic acid and propanedioic acid. Benzoic acid and 2,2-dimethylpropanoic acid need soda lime or more drastic conditions.