Gravity , Explosion
<u>Explanation:</u>
Nebulae are made of dust and gases—mostly hydrogen and helium. The dust and gases in a nebula are very spread out, but gravity can slowly begin to pull together clumps of dust and gas. As these clumps get bigger and bigger, their gravity gets stronger and stronger.
Eventually, the clump of dust and gas gets so big that it collapses from its own gravity. The collapse causes the material at the center of the cloud to heat up-and this hot core is the beginning of a star.
An isotope of any element is the same, with a variation in the neutrons of the nucleus.
The mass number change but the atomic number doesn't.
In this case, protium, deuterium, and tritium are all hydrogen isotopes.
Protium is 1H or Hydrogen-1 is without neutrons.
Deuterium is 2H or Hydrogen-2 has one neutron.
Tritium is 3H or Hydrogen-3 has two neutrons.
Answer:
A. Blood is pushed through vessels
Explanation:
Heart muscles contract and relax. The most important effect of this action on the human body is Blood is pushed through vessels.
Hope it will help :)❤
Viruses go around in the air and bacteria you have to touch
Answer:
The secondary immune response is the immune response when the same antigen , memory cells that was encountered before is remembered and the immune system make antibodies to counter it.
Explanation:
There is a difference between the primary immune response and secondary immune response.
In the primary immune response occur when the immune system encountered an antigen for the first time which lead to the generation of memory cells and and the B cells with the T cells produce antibodies.
While the secondary immune response occur when the same antigen that was encountered the first time is encountered the second time and it lead to the stimulation of memory cells to produce more and high quantities of antibodies to fight foreign substances.
