Why Is There a Trend for Companies to Hire Older

Why is there a trend for companies to hire older workers, particularly on a part-time basis?

A) They need the expertise older workers bring.
B) The type of benefits older workers may (or may not) need might make them less expensive employees.
C) Older workers are more flexible in terms of hours.
D) All of these are reasons why hiring older workers is a good option for many companies.