Concept:The word "strategic" means carefully planned to achieve a particular aim.Explanation:The union president calls the boycott of classes a deliberate action to make their demands heard."Tactical" means carried out as a calculated step to gain an advantage, which is closest to "strategic"."Acceptable" means tolerable, "ethical" means morally right, and "practical" means sensible or realistic, but none imply careful planning or manoeuvring.Therefore, "tactical" best fits the meaning in this sentence.Answer:D. tactical