Which of the following is the main drawback of peer-group comparisons?

a. Depending on the company, it can be difficult to indentify appropriate peers.

b. Peer-group comparisons only work when there are data on two or more peers available.

c. Only pure play companies can be compared

d. Peer-group comparisons always provide a worse benchmark than time-series comparisons.

e. Economy-wide effects, like pandemics or wars make peer-group comparisons unreliable.