Correct Answer & Explanation
Option C
• The phrase 'since last week' indicates a duration of time starting in the past and continuing up to the present.
• When an action or state began in the past and continues into the present, the Present Perfect Tense or Present Perfect Continuous Tense is used.
• Since 'be' (ill) is a stative verb, it typically does not take continuous forms. Therefore, the Present Perfect Tense is appropriate.
• The structure for Present Perfect Tense is Subject + have/has + V3 + Object. Here, 'been' is the V3 of 'be'.