By Modals, Simple past

This is not a present perfect. It is a modal construction; the modal is "may". In this context, "may"* means "it is possible that ... ". Thus, "We believe they may reach the island on a raft" is "We believe that it is possible that they will reach the island on a raft". And "We believe they...

Sharad, Sharad! You are getting yourself tangled up here! Let's see how we can get you untangled. He has had to live or die situations. He had had to live or die situations. He had have to live or die situations. None of these is exactly right. You want to include the idea of...

Both are fine. Use of the modal suggests the immediacy of the activity of changing offices, where the simple past suggests the accomplished fact. It is a perspective in the mind of the speaker/writer which does not normally or materially affect the message conveyed to the listener/reader. If...

I don't really understand the question either... Konstantin, you're referring to the Conditional with your German example. Indirect speech in German works differently as the Conjunctive has to be used in formal German, which however, can be replaced by the Conditional (would+infinitive). In...

As far as I know, there are these 13 tenses: a) Past Perfect Progressive ........................had been + present participle b) Past Perfect ..........................................had + past participle c) Past Progressive ...................................was/were + present participle d)...