The correct use of 'by + future time' is to express an action that will be completed before a certain future point in time. The correct structure is 'will have + past participle'. Option B correctly follows this structure. Option A uses the simple future tense, which does not imply completion by a certain time. Option C uses the present perfect tense, which is not appropriate for future time reference. Option D incorrectly combines 'since' with 'by', which is grammatically incorrect.