diff --git a/routes/openai_route.py b/routes/openai_route.py
index 2786039..316b745 100644
--- a/routes/openai_route.py
+++ b/routes/openai_route.py
@@ -1,4 +1,5 @@
 from fastapi import APIRouter, Response, HTTPException
+from data_access_layer.topics_db_functions import get_topics
 from globals import globals
 from data_access_layer import users_db_functions
 from services.openai_service import get_question_and_answer, evaluate_answer
@@ -16,10 +17,14 @@ async def gen_question(body: GenBody, response: Response):
     max_attempts = 5
     attempts = 0
     
+    allowed_topics = get_topics()
+    if body.topic not in allowed_topics:
+        raise HTTPException(status_code=400, detail=f"Invalid topic: {body.topic}. Must be one of {allowed_topics}.")
+
     try:
         while attempts < max_attempts:
             answer = get_question_and_answer(topic, difficulty, answers_num)
-            if answers_num == len(answer['Answer']):
+            if (answers_num and answers_num == len(answer['Answer'])) or (not answers_num and len(answer['Answer']) == 1):
                 return answer
             attempts += 1
             
@@ -30,7 +35,6 @@ async def gen_question(body: GenBody, response: Response):
         response.status_code = 400
         return {"error": str(e)}
 
-
 @router.post('/evaluate')
 async def evaluate_question(body: QARequest,ai_answer:str, response: Response):
     try:
@@ -41,9 +45,10 @@ async def evaluate_question(body: QARequest,ai_answer:str, response: Response):
         answer = body.answer
         evaluation_score = evaluate_answer(question=question_text, answer=answer,ai_answer=ai_answer)
         users_db_functions.add_user_stats(user_id=user_id, question_text=question_text, answer=answer, topic=topic,
-                             difficulty=difficulty,
-                             score=evaluation_score["Score"], answer_correct=(evaluation_score["Score"] >= 5),
-                             client=globals.mongo_client)
+                                          difficulty=difficulty,
+                                          score=evaluation_score["Score"],
+                                          answer_correct=(evaluation_score["Score"] >= 5),
+                                          client=globals.mongo_client)
         evaluation_score["question"] = question_text
         evaluation_score["user_answer"] = answer
         return evaluation_score
diff --git a/tests/test_openai_service.py b/tests/test_openai_service.py
index 732a820..e845992 100644
--- a/tests/test_openai_service.py
+++ b/tests/test_openai_service.py
@@ -70,6 +70,13 @@ def test_question_generation_wrong_difficulty():
     response = requests.post(url, json={"topic": "python", "difficulty": "HARD"})
     assert response.status_code == 422
 
+def test_question_generation_invalid_topic():
+    server_url = os.getenv("SERVER_URL")
+    assert server_url is not None
+    url = f"{server_url}/question/generate"
+    response = requests.post(url, json={"topic": "invalid_topic"})
+    assert response.status_code == 400
+    assert "Invalid topic: invalid_topic. Must be one of" in response.json()['detail']
 
 def test_gen_question_answers_num():
     server_url = os.getenv("SERVER_URL")