Carcinogenicity and Toxicity

It may vary, depending on the type of substance you are talking about. Some can have their carcinogenic/toxic levels reduced and some may not. Some processes involve detoxification, overheating, altering the chemical structure etc. You can also yourself avoid exposure to these substances by adopting healthy lifestyle habits like jogging, yoga, exercising, sports, meditation etc. and staying away from cigarettes, alcohol, tobacco and others.

There exist different types of cancer, some of which have a remedy to be treated and some of which may never have in the near future. Technologies have advanced, the field of Science and biomedical sector have witnessed significant improvements in the previous decades. Many cancers which seemed impossible to be treated years ago have today a reliable cure. So it depends on which type of cancer and which stage of cancer are you specifically talking about.

Yes. Indeed there are various scientists who are trained to prepare and handle these carcinogens safely in a laboratory. These carcinogens are used to prepare various useful substances such as drugs and medicines so their usage needs to be monitored regularly and handled carefully. The production must comply with legal rules and standards.

In this carbocation +M effect of -OCH₃ group stabilizes the carbocation.

While in option (A) and (B), +M of -OCH₃ will not work but in option (C), +M of -OCH₃ works so due to more delocalization in option (D), it is more stable.