The correct answer is - d. colder and denser.
The main differences between the surface currents and deeper currents are the temperature and density, and that actually decides their position in the water, on the surface, or deeper.
The surface currents are warmer, and because they are warmer the molecules are much more loose, so the density is lower, which in return makes it easier, thus it is in the surface.
The deeper currents are colder, and because they are colder the molecules are much closer and more concentrated, so the density is higher, which means that they are heavier, thus fall deeper below the easier currents.
the area with low pressure will be more dense in the area with high pressure will be less dense
Oil still plays an important role in the global economy despite the continued efforts to reduce its use and to find alternative green energy sources. In the early days, finding oil during a drill was considered somewhat of a nuisance as the intended treasures were normally water or salt. It wasn't until 1847 that the first commercial oil well was drilled in the Absheron Peninsula, Azerbaijan.1 The U.S. petroleum industry was born 12 years later, in 1859, with intentional drilling near Titusville, Pennsylvania. (Drilling in the United States began in the early 1800s, but they were drilling for brine so any oil discovery was accidental.)2
Answer: In Medieval Europe, knights pledged loyalty to vassals, who in turn pledged theirs to powerful lords, and serfs labored in the fields.
Explanation:
A rigid hierarchy refers to one where people who are born into a certain position in life, find it quite hard to move from it or rather one where there are different social classes and people had to be classified in one class for the system to work.
The system during medieval times was much like this. Social classes existed that determined a person's worth in society such as the knights, vassals, Lords and Royals. There was also the serfs who were considered the lowest in the hierarchy.
