Passenger trains often feature self-propelled carriages (multiple units) that can be joined with other units. Trains such as these are more energy efficient but may require more maintenance than a single locomotive vehicle.
Some plants are carnivores, gaining nutrients by eating various small insects and spiders. A well known example of a carnivorous plant is the Venus Flytrap.
Alkali metals such as sodium, potassium, rubidium, caesium and francium are extremely reactive elements, just putting them in water can result in an explosion! They are carefully stored in oil to prevent this happening.
While aluminum is the most common metal found in the Earth's crust, the most common metal found on Earth is iron, mostly because it makes up such a large part of the Earth's core.
