Mary's grandpa is always ______ in the mountain village. He tells her he feels very______. So she's going to visit him next week.
A:alone; alone
B:lonely; lonely
C:lonely; alone
D:alone; lonely
空间技术的发明和应用是第三次科技革命的主要标志之一。标志着中国在空间技术领域跻身于世界先进国家行列的事件是( )