Why is it that once a person starts taking alcohol or drugs,it is difficult to get rid of this habit? Discuss.

The final stage of drug addiction is represented by the need of the drug for the body. This is known as

Identify the correct statements from the following:
$(i)$ With repeated use of drugs,the tolerance level of the receptors present in the body increases.
$(ii)$ Youngsters often use drugs repeatedly due to financial gains.
$(iii)$ Lack of proper guidance or counseling leads individuals to become addicts.
$(iv)$ Repeated use of alcohol leads to 'withdrawal syndrome'.

$A$ well-known painkiller is .........

$A$ psychological and emotional need of a drug-using person is known as:

From which of the given plants is the drug whose skeletal structure is given below extracted?