If the sperm cell fertilises the ovum, and implantation does not occur, then the corpus luteum degenerates and it turns into corpus albicans, stopping progesterone secretion. If fertilisation occurs and implantation also, the syncytiotrophoblast, the "root part" of the blastocyst (one of the early structures originated from the zygote), produces a hormone that is called <span>human chorionic gonadotropin (hCG). The hCG is what makes the corpus luteum keep secreting progesterone and maintain itself. The progesterone will then help keep the endometrium and, therefore, allow the development of the embryo to happen.</span>
Answer:
D. Ultraviolet rays from the sun are prevented from reaching Earth.
surface.
Explanation:
What little is known is that the Earth's magnetic field creates the so-called "magnetic shield" that provides protection against some other dangerous forms of radiation, namely cosmic rays and solar wind.
While there is no danger of losing the Earth's gravitational field, the Earth's magnetic field is declining faster than any other geophysical phenomenon. This continuous loss of the Earth's magnetic field, and the associated increase in harmful radiation, are beyond human control.
Answer:
c) solar energy is renewable because it will be available as long as the sun continues to burn
To be specific, it's indistinguishable
The answer is b. the germ theory of disease.
Louis Pasteur proposed that some diseases are caused by germs in the XIX century.
The concept of atomic weight was proposed by John Dalton. Benjamin Franklin proposed a simple theory of electricity, which was later compounded by Charles du Fay. The theory of evolution was proposed by Charles Darwin.
