Answer: Option D. -> respiration
:
D
Respiration involves breakdown of glucose. It produces carbon, water and releases energy in the form of ATP. It is a biochemical process and takes place inside the cell.The releasedenergy is utilized for various metabolic activities.

Answer: Option C. -> Ingestion → Digestion → Absorption → Excretion
:
C
Digestion process involves the following steps -
$\bullet$ Ingestion or the process in which food is taken in the body.
$\bullet$ Digestion or the process in which complex food particles are broken down into simpler substances.
$\bullet$ Absorption or the process in which the digested food is absorbed into the body.
$\bullet$ The byproducts of metabolic reactions which are not useful for the body are eliminated through the process called excretion.

Answer: Option A. -> mouth
:
A
The digestion process of food begins in the mouthby the enzymes present in the saliva. Thefunctions of saliva include moistening food, and helping to create a food bolus, which can be swallowed easily. Salivary amylase is an enzyme in saliva that breaks down complex molecules such as starch into simpler molecules. Hence, digestion process begins from the mouth.

Answer: Option C. -> 3 → 1 → 2
:
C
Each kidney has a large number of filtration units called nephrons, packed close together. Some substances in the initial filtrate are selectively reabsorbed as the urine flows along the tubular part of the nephron. The urine formed in each kidney eventually enters a collecting tube, the ureter, which connects the kidney to the urinary bladder. Urine is stored in the urinary bladder until the pressure in the expanded bladder leads to the urge to pass it out through the urethra.

Answer: Option B. -> Diffusion
:
B
Diffusion is the movement of a substance from an area of high concentration to an area of low concentration. Theexchange of gases takeplacein the millions of alveoli in the lungs and the capillaries that envelop them. Due to the difference in concentration, inhaled oxygen moves from the alveoli to thebloodin the capillaries, and carbon dioxide moves from thebloodin the capillaries to the air in the alveoli.

Answer: Option B. -> Stomach and small intestines
:
B
The digestion of proteins starts in the stomach by the action of gastric juices produced by the walls of the stomach. Further, it also takes place in the duodenum and ileum of the small intestine under the action of pancreatic and intestinal juices respectively.

Answer: Option D. -> Both statement 1 and statement 2 are false
:
D
Lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released. Some volume of air is present in the lungs even after forceful expiration.

Answer: Option B. -> Stored in the form of starch for future use.
:
B
Excess or unused carbohydrates produced during photosynthesis are stored in the form of starch (polysaccharide/polymer of simple glucose molecules) as a reserve of energy for future use in various parts of the plant body.

Answer: Option B. -> Valves
:
B
Veins collectblood from different parts of the bodyand bring it back to the heart. They do not need thick walls because the blood is no longer under pressure, but instead, they have valves toensure that the blood flows only in one direction towards the heart.

Answer: Option B. -> Alveoli
:
B
$\bullet$ The alveoli are surrounded by tiny blood vessels, called capillaries. It is the alveoli that receive the oxygen and pass it on to the blood.
$\bullet$ Alveoli and capillaries both have very thin walls, which allow the oxygen to pass.
$\bullet$ Trachea, also called the windpipe, is a cartilaginous tube that connects the pharynx and larynx to the lungs.
$\bullet$ Nostril is either of the two external openings of the nasal cavity that allowsair to enter the lungs.
$\bullet$ Bronchi arethe air passages into the lungs.