Jawabannya;

a. When I phoned my friends, they were playing monopoly.

b. Yesterday at six I prepared dinner.

c. The kids were playing in the garden when it suddenly began to rain.

d. While Alan was working in his room, his friend called him.

e. I was listening to the radio while my sister was watching.

Penjelasan;

Secara singkat, kalo jawab soal gini tu kita harus membayangkan kejadiannya. (Btw ada gambar saya lampirkan ttg beda past simple dan past continuous).

Misal nih, soal a, "waktu aku nelepon temenku, dia lagi main monopoli". Nah, kata "while" itu menandakan dia sedang berlangsung ketika ada aktivitas yang ganggu (nelepon).

Same case kayak c, "anak-anak lagi pada main di kebon dan tiba-tiba hujan". Si anak tu lagi main (continuous), terus ada aktivitas menginterupsi (hujan)

kalo soal yang d, "selagi Alan nugas di kamarnya, temennya manggil". Si Alan ni lagi nugas (continuous), terus ada aktivitas ngeganggu (di panggil temennya).

Kalo yang e, "aku lagi dengerin lagu di radio sementara my sister lagi nonton". Jadi mereka ini sama sama lagi ngelakuin activity, gak interrupting satu sama lain.

Kalo yang b, karena udah dikasih tau exact time nya, jadi pake past simple. Dia itu completed action. Exact time dan completed action itu salah satu ciri past simple.