In linguistics, intonation is variation of pitch while speaking which is not used to distinguish words. It contrasts with tone, in which pitch variation does distinguish words.
So when your voice rises at the end of a question, that is technically called intonation.
Inflection has two meanings: it can sometimes mean intonation, as Dictionary.com shows:
modulation of the voice; change in pitch or tone of voice.
However, Wikipedia defines it exclusively as the form of a word, and not the sound:
[I]nflection ... is the modification of a word to express different grammatical categories such as tense, grammatical mood, grammatical voice, aspect, person, number, gender and case. Conjugation is the inflection of verbs; declension is the inflection of nouns, adjectives and pronouns.
Since inflection is ambiguous and not the correct technical linguistics term, it would be better to use intonation, so everyone can understand what you're talking about.
This is a hard question, and there is a lot of idiom involved.
The cases where you can be reasonably sure that "make" is right is
when you are creating something:
"make a salad", "make a home", "make
a mess", "make a film".
when you are causing somebody or
something to do something: "make
somebody listen", "make him stop",
"make the book stay open"
when you are causing somebody or something to be a certain way: "make him late", "made me happy".
"Do" tends to be more general, and tends not to be used in the cases above (and is rarely used with a direct object except for a word like "job" or "task" - but see below).
"Do" is also used as "pro-verb" in questions and replies, standing for almost all verbs, including "make": "What did you do?" "I made a cake".
But there are many idiomatic cases which are not obviously predictable. We "do" the shopping, the washing ("do the laundry" in the US, I believe), the dishes, the windows (i.e. clean them), our homework, our tax return; but we "make" the bed (i.e. arrange the bedding neatly).
Here are the definitions, not for products but for human competence, according to the DOD.
What is Suitability? Suitability refers to a person’s identifiablecharacter traits and conduct sufficient to decide whether employment
or continued employment would or would not protect the integrity or
promote the efficiency of the service.
What is Fitness? Fitness refers to the level of character and
conduct determined necessary for an individual to perform work for,
or on behalf of, a Federal agency as an employee in the excepted
service (other than in a position subject to suitability) or as a
contractor employee.
If I understand well, and adapted for a product, suitability, would be, for example, that a knife is suitable to cut a steak (whatever the state of its blade) but could not be called fit to cut the steak if it's not sharp enough to do the job.
It's might be confusing though. The author seems to say that suitabilty is the continuation, a more modern verson of fitness but in the body of the text he sometimes uses the term as synonyms...
Best Answer
Intonation would be the most fitting:
So when your voice rises at the end of a question, that is technically called intonation.
Inflection has two meanings: it can sometimes mean intonation, as Dictionary.com shows:
However, Wikipedia defines it exclusively as the form of a word, and not the sound:
Since inflection is ambiguous and not the correct technical linguistics term, it would be better to use intonation, so everyone can understand what you're talking about.