The correct answer is D. Secret and unfair influence.
Backstairs influence is a type of secret and unfair influence that is used to get something that you do not deserve. It is often used in politics and business to get ahead of others.
Political influence is the power that people have to affect the decisions that are made by the government. It can be used to get things done that would not be possible without it.
Backing influence is the support that someone has from other people. It can be used to help someone get a job or to get into a good school.
Deserving and proper influence is the influence that someone has because they are qualified for something. It is often used to get a job or to be elected to office.
In the given question, the man is using backstairs influence to get the job, even though he has failed the written examination. This means that he is using secret and unfair means to get the job, which is not deserving or proper.