“an unobstructed passage to the Atlantic”
This "unobstructed passage to the Atlantic" allows for access "to every quarter of the world." The ability to reach every part of the word allows for Britain to trade with anyone and everyone. It best supports the thesis that Britain's geographic advantages supported trade. The detail "insular [inward looking] situation" makes Britain seem closed off as it is focused on it being inside itself rather than open to others. "Combined with the command of the seas" indicates that Britain has access to the seas, but doesn't show how far reaching it goes. "Secures our territory from invasion" would be better to prove that Britain is well protected and safe from invading forces.
Letter A! The "A.M." Is (obviously) a time (morning!) fun fact A.M. Stands for ante meridiem (ante is Latin for before and meridiem is Latin for middle) :)
Mercutio tell the boys to just have fun at the party
4. The prepositional phrase in this sentence is "in an area", the subject is "The blast", and the verb is "flattened"
5. The prepositional phrases are "in Russia" and "to the remote region", the subject is "political events", and the verb is "delayed".
6. The prepositional phrase is "in 1927", the subject is "the first researchers", and the verb is "explored"
7. The prepositional phrases are "by the extent" and "of the devastation", the subject is "They", and the verb is "were amazed"
8. There are no prepositional phrases in this one, the subject is "no crater", and the verb is "was found"
9. The prepositional phrases are "of times" "than an atomic bomb", the subject is "scientists", and the verb is "estimated".
10. The prepositional phrases are "after exploring many theories", "about five or six miles", and "above the Earth", the subject is "most scientists", and the verb is "believe".
I hope this helps you out! :-)