The correct answer is the first one: Steel structures are now stronger than at any other time.
This is the only sentence that makes a good comparison between structures from different times. It compares structures from today and structures from the past. The word "at" is used to express the time when an event takes place so it clarifies that we are talking of the structures from another time period.
The other options fail on comparing structures from different times as they don't use "at", they compare the structures to time itself: "stronger than any time." Here the sentence states that steel structures are stronger than time wich doesn't make any sense.
A complex sentence has an independent clause and one or more dependent clauses. Ex: When the cake is brown, take it out of the oven. The first part of this sentence is a dependent clause because it is not complete by itself. The second part is independent because it can stand on it's own. Hope this helps!
ARMY!! Anyway if you don't have a magazine you find a ton of magazines online, you can save the images either by screenshotting or saving them and cite the websites you got them on on a separate piece of paper. I'm sure your teachers will understand
