B. The opinions may provide clues to the source's feelings and possible bias
Explanation:
History helps to unravel the past so as to better understand the present and predict the future to a logical extent.
The primary sources usually gives the eye witness account about an event. The information here is usually original and raw in terms of quality. Some examples are reports of experiments, records, etc. Most facts are usually drawn from primary sources.
Secondary sources are second hand information about an incidence. Most news reports and newspaper accounts are secondary sources of information. They represents opinions about a happening.
Opinions gives investigative and thoughtful perspective about most primary sources of historical data. They provide a keen thought about possible bias and feelings of the actual description of the original evidence.
Answer:
Petroleum is oil from the remains of water organisms, the oil can be found beneath the ocean floor. Petroleum is a crude oil, and is made of pure chemical compound.
Solar energy has been one of the best inexhaustible resources. There are already some studies and inventions of containing this energy through solar panels. Right now there are a lot of electrical appliance inventions having low energy consumptions that can function well like led. Solar energy can be enough to support electric appliances with this technologies. In addition to this, wind energy has proven to be effective in different countries.
