All of them sound natural to me except #6. I would say instead:
Why is my stomach burning?
or
What is making my stomach burn?
One other note, though; even though Nos. 1-4 are worded okay, I would not call those "stomach problems." The phrase stomach problems is usually used to describe ailments like indigestion, as you did in Nos. 5 - 8. A growling tummy isn't really a stomach "problem," not in the way I usually hear stomach problems.
Is there any other word which is commonly used to describe stomach related problems?
There probably are, although I think you nailed the two most common ones with Nos. 7 & 8. Upset is often used when referring to the stomach organ, while bloated is sometimes used when referring to the lower abdomen in general, and may not be related to digestive problems at all. Sometimes you might hear the term GI used, particularly in the medical community (GI being short for gastrointenstinal). You can simply Google GI problems for a boatload of examples.
First, I'll put on a veneer of scientific-ness and consult a corpus!
I searched the Corpus of Contemporary American English (COCA) for alien. That had 8783 results, which is a lot more than I intended to look at, so I clicked the SAMPLE: 100 link to get a random sample of 100 results. (The order of the first 100 results is not random by default, so that's a helpful thing to do.)
Looking at those results, here's what I noticed:
- Alien by itself usually means space alien.
- Alien is used sometimes in legal contexts, usually in terms like legal resident alien or illegal alien, though it does occasionally appear by itself.
- When people are described as "aliens", it's often put in quotes as though it's an unusual term.
Although these results are based on a corpus of published material, these observations fit my intuition about how the term is used in American English. Personally, as a speaker of American English, if I heard your sentence:
Aliens are surprised when I tell them I don't have a television.
I'd assume you meant space aliens, and this assumption is supported by the corpus results I looked through.
And now for my opinion:
My personal impression is that the term alien is very "other-izing". It's a term that makes whatever you're describing feel very different and unfamiliar. My feeling is that it's not appropriate to apply to people outside of specialized contexts precisely because people aren't "other" enough. We're all humans, after all!
If my impression is correct, it might follow that xenophobes (people who fear the "other") are more likely to use this term to describe people. And for both of these reasons, I think it's possible that people could feel marginalized by the term or take offense to it. So to me, it feels like it's best to avoid using alien this way.
My guess is that this is true outside the U.S. as well, but I don't really know.
Best Answer
"Visualization" is the only correct spelling in American English.
"Visualisation" and "visualization" are both acceptable in British English although it is a common misconception that "visualization" is an Americanism and therefore incorrect.
Oxford resolutely prefers "ize" forms - see visualize in the British English Oxford Dictionary - and a lot of academic writing follows their lead but most mass market publications prefer "ise".
There's more information in Wikipedia and an interesting article with further references.