A person with strong sexual urges, who channels his energy into religious fervour, presents a classical example of:-

Reaction formation

The correct answer is Reaction formation.

In projection, people attribute their own traits to others. Thus, a person who has strong aggressive tendencies may see other people as acting in an excessively aggressive way towards her/him.

In denial, a person totally refuses to accept reality. Thus, someone suffering from HIV/AIDS may altogether deny her/ his illness.

In reaction formation, a person defends against anxiety by adopting behaviours opposite to her/his true feelings. A person with strong sexual urges, who channels her/his energy into religious fervour, presents a classical example of reaction formation.

In rationalisation, a person tries to make unreasonable feelings or behaviour seem reasonable and acceptable. For example, when a student buys a set of new pens after doing poorly in an examination, s/he may try to rationalise her/his behaviour by asserting, “I will do much better with these pens”. People who use defence mechanisms are often unaware of doing so.

Each defence mechanism is a way for the ego to deal with the uncomfortable feelings produced by anxiety.