Institution: Directorate of Primary Education - DPE Exam: Primary Exam Question Solution 21-06-2019
Topic: Preposition, Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The correct choice in the sentence "The ambassador called —— the president" is "C) on." This choice reflects a specific usage in English that indicates making a formal or scheduled communication.

When we say someone "called on" someone else, it often implies a visit or a formal request for a meeting or discussion. In diplomatic contexts, as with an ambassador, the phrase conveys the notion of paying a visit to another official, such as the president, to discuss relevant matters or policies. It suggests that the ambassador is engaging in official diplomacy, a key aspect of ambassadorial duties.

On the other hand, "called at" (option A) is less common and generally refers to a more casual or informal visit, which may not suit the formal context implied here. "Called in" (option B) can suggest a brief visit or a quick communication but does not convey the same level of formality or the implied significance of an ambassador meeting with a head of state.

Overall, "called on" is the most appropriate and contextually correct option, denoting the formal nature of the ambassador's communication with the president.