Answer:
H.
Step-by-step explanation:
The letter in the Spanish alphabet that is silent is the letter H. It is never pronounced except when a word has a C before the H. For example: ‘Chaleco’ which means ‘waistcoat’.
However, it is helpful in the Spanish alphabet for many reasons, such us marking a hiatus in some words. An example of this case is the word ‘búho’ (translation: owl).