A present tense verb refers to verb forms used to express actions that occur in the present or now, this also applies to facts. This tense includes the simple present tense, in this, verbs follow the infinitive form without "to" and in the case of the third person singular (she, he, it) verbs end in -s or -es. For example "I go to the park every day" or "She eats a sandwich".
The sentence "I surf" contains a present tense verb that is "surf" because this verb follows the infinitive form "to surf" (without to) that is used in the present tense. Also, other options are not correct because "I went surfing" and "I surfed" contain a past tense verb and "I will go surfing" contains a future tense verb.
