Read the text below about "green"school. Complete the text with the right tense of the verbs in brackets in the passive or active form. Solar panels 1___(install) on the school roof in 1999. Two years later, we 2___(introduce) waste separation for paper, glass and plastics. A small wind turbine 3___(build) on a hill just outside the school by a physics class. For over five years now all the lights 4(control) by sensors. At the moment some special software 5___(load) onto all school computers, so they shut down automatically at the end of the day. Drinks that 6___(sell) by machines are cheaper if you 7___(use) your own cup, but the machine also 8___(give) money back if its plastic cups 9___(return). Snacks which 10___(buy) in the school shop 11___(not warp). Plants for the future? Hopefully, paper 12___(save) when we 13___(start) sending letters to parents by email only.

Solar panels were installed on the school roof in 1999. This means that in 1999, someone came and put solar panels on the roof of the school. Solar panels are devices that use the sun's energy to create electricity. By installing solar panels, the school can use clean and renewable energy to power its appliances and lights.

Two years later, waste separation was introduced for paper, glass and plastics. This means that after two years, the school started separating its waste into different categories - paper, glass, and plastics. Waste separation is important because it allows us to recycle and reuse different materials instead of throwing them away. By doing this, the school is promoting environmental sustainability and reducing the amount of waste sent to landfills.

A small wind turbine was built on a hill just outside the school by a physics class. A wind turbine is a device that converts the wind's energy into electricity. The physics class decided to build a wind turbine, probably as a project or experiment. This wind turbine can generate electricity using the power of the wind.

For over five years now, all the lights have been controlled by sensors. This means that for more than five years, the lights in the school have been automatically turned on or off by sensors. Sensors are devices that can detect movement or the absence of it. When there is no one in a room, the sensors turn off the lights to save energy. This is a great way to reduce electricity consumption and save money on utility bills.

At the moment, some special software is being loaded onto all school computers. This means that right now, someone is installing or putting a special software on all the computers in the school. This software is designed to make the computers shut down automatically at the end of the day. By doing this, the school can save energy and ensure that the computers are not left on overnight or when they are not being used.

Drinks that are sold by machines are cheaper if you use your own cup, but the machine also gives money back if its plastic cups are returned. This means that if you bring your own cup to the machine to buy a drink, it will be cheaper for you. Using your own cup is a great way to reduce the use of disposable cups, which are made of plastic and can harm the environment. However, if you do use the machine's plastic cups, the machine will give you money back if you return them. This is a clever incentive to encourage people to recycle and return the plastic cups instead of throwing them away.

Snacks that are bought in the school shop do not warp. This means that when you buy snacks from the school shop and take them home, they do not become damaged or twisted. Sometimes, snacks that are not packaged properly can get squished or crushed, but the snacks from the school shop remain in good condition. This is important because it ensures that the snacks are still enjoyable to eat and not wasted due to damage.

In the future, hopefully, paper will be saved when we start sending letters to parents by email only. This means that in the future, when the school decides to send letters to parents, they will do it through email instead of using paper. By doing this, the school can reduce its paper consumption and promote a more eco-friendly way of communicating. Email is a fast and efficient way of sending information, and it also helps to save trees, as paper is made from wood.