Which is a complex sentence?

they will not defeat their enemy until they come up with a better strategy.

the castle is a fortress, but it does have some weaknesses.

with its calm surface, the moat looked harmless, but it had hidden dangers.

watchful archers hid in the towers, and the soldiers stood ready below.

m

explanation:

greet them:

buenas noches.

that is considered night time which is when "good night" is used.

martians or other types of aliens represent a unique fear as opposed to zombies. vampires and other types of monsters.   in most sci-fi stories, aliens come from other worlds and have different or more advanced technology.   abductions and experimentation on human bodies that involve these technologies, or the use of these technologies against human beings and the use of unknown "powers", are a type of fear that's different from that of other types of monsters.  

from the political point of view it could be said that the candidate   is an effective speaker because she takes a strong position on the issue. it is an open discussion but probably she is making a presentation and can choose which subjects she wants to address. she is very likely to attain her aim which is to convince voters to accept her proposal.