<span>A is the correct answer. Diploid cells all contain two sets of chromosomes. Prophase 1 occurs during the first phase of meiosis, a type of cell division, and prophase 2 is the same process, but this time occurring without chromosome reduplication. As a result, there is the original and duplicated cells, which makes two.</span>
Answer:
"Option B. The tilt of the moon´s orbit around the earth
" limits the number of eclipses per year
<u>Explanation</u>:
The moon's orbit is tilted only by 
. Around the sun when the earth and moon move, the tilt of the moon changes according to the direction of the sun. When the same thing occurs to the earth, the seasonal changes occur. The theory is all related to moon's formation. Due to this tilt the moon's road near the stars changes slightly in every month. The inclination is with respect to the ecliptic plane. If this inclination was absent then we could have felt the eclipse more frequently.
Parkinson's disease
<span>Parkinson's disease results from deterioration of brain's nerve cells</span>
<span>a. Fish have a single central heart; earthworms have several hearts.
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Multi cellular organisms are made up of billions of cells each specialized to a unique role and these cells are organized into structural and functional units such as tissues and organs.
For each cell and organ to function optimally, it requires oxygen and nutrients and needs carbon dioxide and metabolic waste taken away in a continuous, never ending process.
<span>A mechanism is needed to accomplish the important function of transporting the relevant materials to and from the cell. The circulatory system fits this bill splendidly. It is a specialized organ system which allows blood and lymph to flow through the entire body carrying nutrients such as glucose, amino acids and electrolytes as well as oxygen to each cell, at the same time carting away carbon dioxide and all sorts of metabolic waste over to excretory organs to be expelled from the body.
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