I _ English since my childhood.

Explanation

Study: This option is in the present tense, which does not match the time frame "since my childhood." We need a present perfect or past perfect tense to match the time frame. 'Have been' suggests an action that started in the past, but continues in the present. Am studying: This option is also in the present tense and doesn't match the time frame mentioned. It also implies that the action is still ongoing, which may not be the case.Studied: This option is in the past tense, which does not indicate that the action started in the past and continues up to the present moment, as the sentence implies.