Question 21 is based on the recording you have just heard.

21. What do professional social workers have in common, according to the speaker?

解析：B。本题目为细节题。问题为：讲话者认为，专业的社会工作者的共同之处是什么？原文所在句：There are more than 600,000 professional social workers in the country, and we all either have a bachelor’s degree, a master’s degree, or a PhD in Social Work. 全国有超过60万的专业的社会工作者，并且他们都有社会工作专业的学士学位、硕士学位或博士学位。选项B) They all have an academic degree in social work（他们都有社会工作专业的学位），与文中信息相一致。此题目其他选项干扰性较强。A选项的clinical training（临床训练）和C选项的National Association（联合组织）在原文中均出现过，易形成干扰。但若抓住题目中的professional social workers in common能在原文中快速定位。