When the coal reaches its hardest and the darkest form then it is termed as anthracite.
Answer: Option D
<u>Explanation:</u>
The hardest among the coal is called as the anthracite. It has large amount of carbon atoms and it is also regarded as the best quality of coal that is being mined.
This is mostly prevalent in South Korea, North Korea, United states, United Nations, Canada etc. This is mainly used in the steel making process and is combined with many alloys for enhancing their property.
<span>sporangia
</span><span> is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form </span>sporangia<span> at some point in their life cycle.</span>
their cell wall surrounds it and secretes enzymes that encase it into a bubble and brings it into the cell. After other enzymes digest what is needed the process reverses and the bubble is 'spit' out or excreted.
The correct answer is - quartz.
The quartz is a light colored, transparent mineral, with hardness of seven, and is characteristic that instead of cleaves it has fractures. This mineral is composed of silicon and oxygen atoms, which make a tetrahedral structure. It is the second most abundant mineral in the Earth's crust, just after the feldspar.