(a) A vaccine is a biological preparation that provides immunity against a particular disease. It consists of dead or weakened microbes.
(b) Arya would have explained that vaccines on entering the body produces suitable antibodies. These antibodies remain in the body and fight any encounter with the microbe in future. Moreover, vaccines contain dead or weakened microbes, thus they are not harmful.
(c) Arya is an intelligent, helpful and well aware person.

Oil has been poured on the pickle to form a barrier. This prevents the bacteria from attacking the pickle and spoiling it. Thus, increasing its shelf life.

Tuberculosis is an air-borne disease which easily spreads when the infected person coughs as coughing spreads germs in the air. This is why we should avoid standing close to a TB patient

Microorganisms survive under adverse conditions by forming a hard and protective covering called cyst around them. On return of favourable conditions, the cyst wall breaks and microorganisms resume their life cycles.

Antibiotics are tablets, capsules or injections which are used to kill or stop the growth of pathogens, i.e. disease causing microbes. Penicillin, tetramycin are the examples of antibiotics.
Precautions to be taken are
(i) It should be taken in proper doze only on the advice of a qualified doctor.
(ii) Complete course prescribed by the doctor should be taken.
(iii) It should not be taken unnecessarily as it may kill useful bacteria in the body.

We will find the volume of dough has increased. Carbon dioxide produced by yeast has caused the dough to expand and rise.

Fermentation is the process by which yeast converts sugars into alcohol.

(a) Microorganism is bread mould (Rhizopus) and the group is fungi.
(b) Organism grows on moist and stale bread.
(c) It grows well in moist condition.
(d) No, the fungus spoils the bread by producing poisonous substances (toxins).