GRE Text Completion: ETS Official Practice 150-GRE OP150:填空 - 6G567MSPGPXT9LPMO

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 ____________. A. crowded B. invulnerable C. protected D. polluted E. benign