Topic: Conjunction,

Best Answer Explained in Below-:

The question "How long did you wait?" seeks to determine the duration of an individual's waiting period. Among the provided options, "Till he came" (option B) stands out as the most appropriate answer because it directly addresses the completion of the waiting period. This phrase implies that the wait ended when a specific event occurred—namely, the arrival of the person in question.

In contrast, the other options provide vague or undefined time frames that do not effectively encapsulate the concept of waiting until a particular event. For example, "Till lunch time" (option A) suggests a time of day but lacks specificity regarding when the waiting started or what event it was tied to. "Until six o'clock" (option C) similarly focuses on a specific time but does not clarify the motivating factor behind the wait. Lastly, "Since this morning" (option D) indicates the beginning of the waiting period but does not conclude when the wait ended.

Thus, option B, "Till he came," effectively conveys the complete experience of waiting, defining both the duration and the significance of the end point, making it the clear choice.