The correct answer is C. The temperature of the water
Explanation:
In an experiment such as the one described about the speed of snails in water, the manipulated variable is the factor or element that is manipulated on purpose. This means the researcher or researchers slightly change this element to compare how this affects another variable. In this context, the manipulated variable is the temperature of the water because researchers used three different temperatures (cool, room-temperature, and warm), and therefore they manipulated or changed this factor. Moreover, it is expected temperature affects the distance nails move, which is the main variable.
Answer:
Telescope also known as "spyglass"
Explanation:
In 1609, using this early version of the telescope, Galileo became the first person to record observations of the sky made with the help of a telescope. He soon made his first astronomical discovery.
Answer:
b) and c)
Explanation:
Greenhouse gases are gases found in the atmosphere that absorb infrared radiation and trap the sun’s heat, thereby producing an effect known as <em>greenhouse effect.</em> By this natural way, the earth is able to be kept warm at an optimal temperature, to make it habitable for humans and other organisms. These gases referred to as <em>greenhouse gases</em> include, carbon dioxide, methane, water vapour and other trace gases found in the atmosphere. Greenhouse gases could be likened to the glass in a greenhouse that helps in trapping heat to keep the greenhouse warm at optimal temperature necessary for plant growth and development.
Without this natural greenhouse effect caused by greenhouse gases, life on earth would be almost impossible as the earth would almost be covered with ice below 0 degrees Fahrenheit.
The increased level of greenhouse gases we now find in the earth’s atmosphere is responsible for the additional warming of the earth’s surface, causing an enhanced greenhouse effect which results in global warming.
Statement a) cannot be used as an explanation because it is false. Greenhouse effect makes the earth habitable.
Statement d) cannot be used as an explanation because carbon dioxide is not the only greenhouse gas that matters. Water vapour, CFC and methane also have impacts.
<em>Statement b) and c) are the best statements to use in explaining the true nature of greenhouse effect.
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