When we start gazing into the night sky with a telescope soon we’ll be astonished by the

问题补充：

When we start gazing into the night sky with a telescope, soon we’ll be astonished by the realization we and our world are part of this giant system.

A. which

B. whether

C. that

D. as

答案：

A. which

B. whether

(答案→)C. that

D. as

解析：考查同位语从句。we and our world are part of this giant system.是realization的同位语，that在从句中不做成分。