Explanation: Determining the polarity of a storage battery can be achieved by two common methods: 1. **Voltmeter:** A DC voltmeter has marked positive and negative leads. When connected correctly (red to positive, black to negative), it will show a positive voltage reading. If the leads are reversed, it will show a negative voltage (on a digital meter) or deflect backward (on an analog meter), indicating the actual polarity is opposite to how the leads are connected. This method relies on the meter sensing the potential difference and its direction. 2. **Salt water method (electrolysis):** This simple method involves immersing the two battery leads (without them touching each other) into a glass of salt water. Due to electrolysis, hydrogen gas bubbles will form more vigorously at the negative terminal (cathode), while oxygen gas bubbles form at the positive terminal (anode). The terminal with the most vigorous bubbling is the negative one. Since both a voltmeter and the salt water method are effective ways to determine battery polarity, "A & B" is the correct choice.