Answer: A. combustion
Explanation: During complete combustion, carbon and hydrogen react with oxygen (O2) to produce carbon-dioxide (CO2) and water (H2O). The carbon-dioxide produced is released into atmosphere and is utilized for carbon fixation and recycling.
Answer:
C. capillaries connect arteries and veins.
Explanation:
A is false, veins carry blood towards the heart.
B is false because arteries are the thickest blood vessel.
C is completely true
D is false, heartbeat is controlled by electric impulses
Answer:
The correct answer is - They have substances that counteract acids or bases to prevent the pH from changing
Explanation:
All living organisms including humans are water-based systems, which implies that they rely intensely upon liquid equilibria, particularly acid-base equilibria. Hence, all the acid-base and pH ideas we have talked about so far are critical to the chemistry of organic or biological systems.
This is particularly significant for enzyme, which are proteins that go about as catalysts for all major biological reactions. Most enzymes just work inside a specific pH range. Because all natural cycles are subject to pH, cells and creatures must keep up a particular and consistent pH so as to keep their compounds in the ideal condition of protonation they have specific substances that counteract the acid and base to maintain pH.
for instance:
The pH of the Cytoplasm is maintained by the phosphate ion
The pH of the blood is regulated by the bicarbonate ion
The planets in our Solar System formed from the solar nebula – the disc of gas left over from the formation of our Sun. ... The gas giants on the other hand, formed far enough away from the Sun that the temperature was cool enough for these volatile gases to condense, and form these huge, less dense planets
The answer is D. Because it takes light 8 mins to reach the Earth from the sun.