What is a word for a duty or task to be fulfilled?

One way in which the european union encourages trade among countries is through the use of

The specific department of health and human services (hhs) regulations that apply to research with children are known as: subpart b: additional protections for children involved as subjects in researchsubpart a: the common rulesubpart d: additional protections for children involved as subjects in researchsubpart c: protections for children in research

The pka of three different c―h bonds is given below. explain the observed trend in pka. select the single best answer.