Traditionally, the study of planet formation has proved frustrating, as astronomers have never been sure whether their theories apply to other planetary systems. ----. Now, however, the observations of debris discs around stars of different masses and ages are helping to place our solar system in context.

A) Some discs look like gigantic versions of the rings of Saturn
B) Most of the discs, however, could not be seen directly
C) What the recent images show is wonderfully unexpected
D) This is because the solar system is the only known example of a planetary system
E) The dust particles probably result from collisions among asteroids

D derdim, ..... dan sonra However, çözüme ilişkin bulgulardan söz ediyor.Yani seçeneklerde ...dan önce gelen ifadeyi destekleyecek bir cümle aramalıyız.Bu da D şıkkında var.

Traditionally, the study of planet formation has proved frustrating, as astronomers have never been sure whether their theories apply to other planetary systems. ----. Now, however, the observations of debris discs around stars of different masses and ages are helping to place our solar system in context.

D) This is because the solar system is the only known example of a planetary system

B şıkkı tens uyumsuzluğu
"the only known example" , "Now, however, the observations" birbirini tamamlıyor...

Traditionally, the study of planet formation has proved frustrating, as astronomers have never been sure whether their theories apply to other planetary systems. ------. Now, however, the observations of debris discs around stars of different masses and ages are helping to place our solar system in context.

D) This is because the solar system is the only known example of a planetary system

"This is because the solar system is the only known example of a planetary system"

Bencede cevap D gibi ama bunu eleyerek yaptım. "This is because" yapısı ne demek istiyor