Mrs. Okoro … in this school since 1975

Step 1: Analyze the question The sentence is "Mrs. Okoro ____ in this school since 1975." The key clue is the word "since 1975", which marks a starting point in the past.

Step 2: The concept When an action began at a specific point in the past and continues up to now, we use the present perfect tense (has/have + past participle) or the present perfect continuous (has/have been + verb-ing).

• "Since + a point in time" (since 1975, since Monday, since 2010) signals the present perfect or present perfect continuous.
• Simple past ("taught") describes a finished action and does not go with "since".
• Past continuous ("was teaching") describes an action in progress at a past moment, not one that continues until now.
• Simple present ("is teaching") does not link a present action to a past starting point.

Step 3: Test each option

• A. Mrs. Okoro taught in this school since 1975. Wrong. Simple past does not agree with "since".
• B. Mrs. Okoro has been teaching in this school since 1975. Correct. It shows she started in 1975 and is still teaching.
• C. Mrs. Okoro was teaching in this school since 1975. Wrong. Past continuous cannot be used with "since".
• D. Mrs. Okoro is teaching in this school since 1975. Wrong. The present continuous cannot be used with "since".

Step 4: Answer The correct option is B. has been teaching.

Exam tip: When you see since or for (for five years), look for has/have/had been + verb-ing or has/have + past participle. Remember: "since" + a point in time = present perfect."