Answer:
Ad hominem.
Step-by-step explanation:
Propaganda techniques are the devices or techniques used to attack one's opponents. Such techniques are used to influence the readers or listeners, in the hope of appealing to their desires and support.
The given statement is an example of ad hominem because it makes a personal attack on the opponent rather than the argument. The speaker talks of the young age of his opponent, which he states, makes him unsuitable for the job. This argument is based on the capability of the opponent and a personal attack, which makes the whole statement invalid.
Thus, the correct answer is ad hominem.