The word "laissez-faire" is a French phrase that means "let people do as they choose" or "let people do as they want".

It can be used to describe a doctrine, a philosophy, or a policy of minimal or no interference in economic or social affairs.

It can also be used to describe a person's attitude or behaviour that is relaxed, easygoing, or indifferent.

In this context, the word "laissez-faire" is used to describe a person's attitude to work that is careless, negligent, or irresponsible.

It implies that the person does not take their work seriously, does not follow rules or guidelines, and does not care about the quality or outcome of their work.

Therefore, the option that is nearest in meaning to "laissez-faire" is B. care-free. This means having no worries or troubles or showing no concern or interest.

The other options are not as close in meaning to "laissez-faire". A stupid attitude means lacking intelligence or common sense.

A careful attitude means showing attention or caution. A serious attitude means being earnest, solemn, or thoughtful. A responsible attitude means being accountable, reliable, or trustworthy.