A menu loop dispatches to three functions sharing a marks list; grading resolves the given criteria as a top-down ladder:

marks = []
subjects = ["English", "Maths", "Science", "Social Science", "Hindi"]

def accept_and_display():
    marks.clear()
    for sub in subjects:
        marks.append(float(input("Enter marks in " + sub + ": ")))
    for i in range(5):
        print(subjects[i], ":", marks[i])

def percentage():
    if not marks:
        print("Please enter marks first (option 1).")
        return None
    total = sum(marks)
    per = total / 5
    print("Total marks:", total, " Percentage:", per)
    return per

def grade():
    per = percentage()
    if per is None:
        return
    if per > 85:
        g = "A"
    elif per >= 75:
        g = "B"
    elif per >= 50:
        g = "C"
    elif per > 30:
        g = "D"
    else:
        g = "Reappear"
    print("Grade:", g)

while True:
    print("\n1. Accept & display marks  2. Percentage  3. Grade  4. Exit")
    ch = input("Enter choice: ")
    if ch == "1": …

The idea. A menu-driven program is an intentional infinite loop (while True) that shows options, reads a choice, and dispatches with if–elif — exiting via break. Keeping the marks in a list shared by small functions mirrors how the SMIS case study grows chapter by chapter: each menu option becomes one function.

The grade criteria table has two printed quirks we must resolve honestly: percentage exactly 50 appears in both the C row (>= 50) and the D row (<= 50), and percentage exactly 30 appears in neither (D needs > 30, Reappear needs < 30). A top-down ladder settles both: 50 lands in C (its test runs first) and 30 falls through to Reappear.

Program

marks = []
subjects = ["English", "Maths", "Science", "Social Science", "Hindi"]

def accept_and_display():
    marks.clear()
    for sub in subjects:
        marks.append(float(input("Enter marks in " + sub + " (out of 100): ")))
    print("Marks entered:")
    for i in range(5):
        print("  " + subjects[i] + ":", marks[i])

def percentage():
    if not marks:
        print("Please enter marks first (option 1).")
        return None
    total = sum(marks)
    per = total / 5          # 5 subjects
    print("Total marks :", total)
    print("Percentage  :", per)
    return per

def grade():
    per = percentage()
    if per is None:
        return
    if per > 85:
        g = "A"
    elif per >= 75:
        g = "B"
    elif per >= 50:
        g = "C"
    elif per > 30:
        g = "D"
    else:
        g = "Reappear"
    print("Grade       :", g)

while True:
    print()
    print("SMIS - Student Marks Menu")
    print("1. Accept and display marks (5 subjects)")
    print("2. Calculate and display percentage")
    print("3. Find grade")
    print("4. Exit")
    ch = input("Enter your choice (1-4): ")
    if ch == "1":
        accept_and_display()
    elif ch == "2":
        percentage()
    elif ch == "3":
        grade()
    elif ch == "4":
        print("Goodbye!")
        break
    else:
        print("Invalid choice. Enter 1-4.")

Sample run (choices 1 then 3 then 4), marks 90, 85, 78, 88, 92:

Enter your choice (1-4): 1
Enter marks in English (out of 100): 90
Enter marks in Maths (out of 100): 85
Enter marks in Science (out of 100): 78
Enter marks in Social Science (out of 100): 88 …