The temperature of an object is observed to rise in a period. In this period,

Options

A. heat is certainly supplied to it
B. heat is certainly not supplied to it
C. heat may have been supplied to it
D. work may have been done on it

Answer

To solve the question regarding the temperature rise of an object, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Situation**: We have an object whose temperature is observed to rise over a certain period of time. We need to determine what could be happening in this scenario.

2. **Identifying the Options**: The options provided are:
- A) Heat is certainly supplied
- B) Heat is not supplied
- C) Heat may have been supplied
- D) Work may have been done on it

3. **Applying the First Law of Thermodynamics**: The first law of thermodynamics states:
\[ Q = W + \Delta U \]
Where:
- \( Q \) = heat supplied to the system
- \( W \) = work done by the system
- \( \Delta U \) = change in internal energy of the system

4. **Analyzing the Temperature Rise**: Since the temperature of the object is rising, it indicates that there is an increase in internal energy (\( \Delta U > 0 \)).

5. **Considering Heat Supply**: If we assume that no heat is supplied to the object (\( Q = 0 \)), then according to the first law:
\[ 0 = W + \Delta U \]
This implies:
\[ \Delta U = -W \]
Since \( \Delta U \) is positive (temperature is rising), this means that work must have been done on the object (\( W < 0 \)).

6. **Conclusion**: Therefore, the correct interpretation is that work has been done on the object, leading to an increase in its internal energy and thus a rise in temperature. This corresponds to option D: "Work may have been done on it."

### Final Answer:
The correct answer is D) Work may have been done on it.