Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

It's easy to adopt eco-friendly habits, and you can always start at home. Here are three tips to help you.

A. There are so many electrical appliances around us, so if we could save even a little amount of energy from each appliance, it would add up to a lot. For example, there are likely to be tens of light bulbs in your house, so if you can replace them with LED ones, which are more energy-efficient and long-lasting light bulbs, you would save a lot of electricity. Before you buy a new appliance, you should also check its energy star rating which shows how much energy it will use in a year. It's easy to understand: the more stars there are, the more energy you can save!

B. To reduce your carbon footprint, you should also turn off the lights when you leave a room. In addition, keep your windows or curtains open during the day to let natural sunlight in, or place more mirrors near a lamp to maximise lighting in the house. This can also help to reduce both energy consumption and your energy bills.

C. While many people already know that turning off appliances around the house when they finish using them can save energy, they may not know that it is even better to unplug them. It is estimated that we could save up to 10% of our electricity bills every month simply by unplugging appliances when they're not in use. This is especially true for chargers. Many people tend to leave their fully charged phones connected, not knowing that it consumes around 2.24 watts. The figure goes up to 29.84 watts for laptops and computers. Leaving an empty charger plugged in has a similar effect, so make unplugging a habit!

The modern Christmas tree has its ________ in 16th-century Germany. A. custom B. tradition C. origin D. practice