單格填空第 27 題
Most spacecraft are still at little risk of collision with space debris during their operational lifetimes, but given the numbers of new satellites launched each year, the orbital environment in the future is likely to be less ______.
| Blank |
|---|
| (A) crowded |
| (B) invulnerable |
| (C) protected |
| (D) polluted |
| (E) benign |
出處：PP2, Practice Test 2, V1, #2
難度：Medium