Which of the following statements is/are true about problems in client recruitment and retention in experimental and quasi-experimental evaluations in social work agencies?

	a.	Referring agencies might dump clients that they don't want to serve.
	b.	Referring agencies might be reluctant to refer any clients.
	c.	Referring agencies might resent having their referrals assigned to a control condition.
	d.	Clients may resent the use of randomized procedures to determine which service they receive.
	e.	Agency estimates of the number of likely referrals may be overly optimistic.
	f.	All of these