Fill in the gaps. I always ... (believe) in you.

The correct answer is "have always believed". **Explanation:** The sentence requires the present perfect tense because it describes an action that started in the past and continues up to the present moment. The structure of the present perfect tense is "have/has + past participle of the verb". In this case, the past participle of the verb "believe" is "believed". Since the subject is "I", we use "have". Therefore the correct form to fill the blank is "have always believed". The other options are incorrect: * "have always believing" is grammatically incorrect because "believing" is a present participle and cannot be used this way with 'have always'. * "believed" is the past simple tense, which would not express the continuation of the action. * "has always believed" is used with the third-person singular subjects (he/she/it), but here the subject is "I". So, the complete sentence is: "I have always believed in you."