Logic

It really isn't a logic question at all. What it says depends on a lot of extra-logical assumptions about earthquakes, their severity, the location of the city relative to the earthquake area, etc.

I'll disagree with you there. It might not be pointless.Okay, it is pointless in your post, because it is disconnected from everything else. Let me try an example that I once saw. This is from a time before the feminist movement.

1. A woman is either attractive or unattractive;
2. If a woman is attractive, a university education is superfluous;
3. If a woman is unattractive, a university education is inadequate;
4. Therefore, for a woman, a university education is either superfluous or indadequate.

Here, premise (1) is analogous to your assertion about raining.In the argument above, the logic is impeccable. Therefore, if there is a problem with the conclusion, then the problem must be one of the premises.A statement such as "It either is raining outside or isn't." is often used in a syllogism, precisely so that an argument can be given with impeccable logic. But that initial premise is still subject to challenge, so it is not pointless. Rather, it serves the role of separating the logic from the non-logical assumptions being made about the real world. Here I take you as using "opposite" as an ordinary natural language term (with all the vagueness that implies), rather than as a precise logical term. My answer would be that the opposite is a truism or tautology -- something that is always true just due to the nature of the wording. If we were to treat that as a purely logical statement, without regard to the real world meaning of the terms, then it has the form of a contradiction. The statement "pies are tasty or not tasty" has the form of a truism.Your example has the form of a contradiction, yet it is not a contradiction (as you explain). What this illustrates is that natural language is not strictly logical. And that's part of why logic puzzles can be a lot of fun.

No, that's not a tautology. One common definition is that a statement is a tautology if it is true in every possible world. Since I can imagine possible worlds where there is good public health service, but nobody is in charge, your statement doesn't qualify.

Not a tautology. There are possible worlds where there are more than two sexes. Yes, that's a tautology.

There was a math text - unfortunately I have forgotten which - where

It's a lot more complicated with plants and insects, where there can be haploid individuals (only one set of chromosomes). There isn't any obvious reason that there could not be a world with a different sexual arrangement than we have in our world. Right. It is a grammatical term, and technically has nothing to do with biology.

It's not up to us to decide which is more important. You need both parts of the cycle for it to all work.In any case, there isn't an obvious reason that you couldn't have a system with three sets of chromosomes, and three sexes. We just don't happen to have that on this planet.

This isn't a logical fallacy. It's just a fact about married life