Respuesta :
Answer:
1.a. present perfect progressive, 2.c.past perfect progressive, 3. b.past perfect progressive, and 4. d.future perfect progressive
Explanation:
Present perfect progressive tense is formed with the modal Have (or Has for the third person; he/she/it) followed by Been followed by the of the verb in its -ing form. As it is the case in sentence 1 .
Past perfect progressive this formed with the modal Had followed by Been followed by the of the verb in its -ing form. As it is the case in sentences 2 and 3 .
Future perfect progressive tense is formed with the modal Will followed by the modal Have followed by Been followed by the of the verb in its -ing form. As it is the case in sentence 4.