Answer: B
Explanation:
The T helper cell needs to acttivate the T cyctotoxic cell in order for the Tc cell to go do its work.
Once the TC cell is active it interacts with MHC-1 proteins on the surface of the infected host cell, this allows the Tc cell to recignise the host cell and begin secreting cytotoxins (perforins and granzymes) in order to degrade the infected cell and cause apoptosis (controlled cell death)
Echinoderm is the name given to a member of the phylum Echinodermata. They have radial symmetry and this includes sea urchins, sand dollars, sea stars and sea cucumbers. It is suggested that they are related to the chordates which is the answer.
<u>ANSWER:</u>
Scientific explanations are accepted when there is sufficient evidence to prove them right. In addition, scientific explanations must be logical to be acceptable and must match as much evidences as possible.
<u>EXPLANATION:</u>
- Scientific explanations explain something about the natural world by making use of observations and measurements.
- These are usually tentative proposals that need to be verified or proved to be true.
- The observations and measurements must prove the scientific explanation to be true or must support it so that it becomes acceptable.
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.
