In principle you can expect that the categories in different countries may not match. These four terms correspond to public officials in Spain, and their functions are defined in Real Decreto 1837/2000, de 10 de noviembre, por el que se aprueba el Reglamento de inspección y certificación de buques civiles:
https://www.boe.es/buscar/act.php?id=BOE-A-2000-21432

The usual generic term in the UK and other English-speaking countries is marine surveyor, rather than inspector. In the UK they are apparently independent professionals, not civil servants, though of course they have to be qualified and work within current legislation.

"A Marine surveyor (including "Yacht & Small Craft Surveyor", "Hull & Machinery Surveyor" and/or "Cargo Surveyor") is a person who conducts inspections, surveys or examinations of marine vessels to assess, monitor and report on their condition and the products on them, as well as inspects damage caused to both vessels and cargo."
https://en.wikipedia.org/wiki/Marine_surveyor

Expanding the UK to include Ireland, we can find equivalents for your terms. "Inspectores marítimos de radio" (d), for example, are called "radio surveyors" in Ireland, as you can see in this Irish Department of Transport page:

"Panel of Authorised Radio Surveyors
Panel of Authorised Surveyors carrying out statutory radio surveys on Irish sea-going vessels including fishing vessels"
http://www.dttas.ie/maritime/english/panel-authorised-radio-...

And here's a UK page which refers to "machine surveyors", which will do you for (c), as well as "naval architecture surveyors", which I think is probably the best equivalent for (a), since according to the Real Decreto, "inspectores navales" are responsible for checking construction: "Revisión global de los proyectos de construcción, transformación, reparación y grandes reformas [...] seguimiento y supervisión de todo el proceso constructivo del buque y de sus pruebas oficiales":
http://www.kinetic-maritime.co.uk/marine-consultancy

Returning to Ireland, here we have a document by an Irish nautical surveyor, who does seem to be a civil servant:

"Charting of Irish Waters Membership of the IHO
Membership of the IHO
Michael Purcell
Nautical Surveyor
Marine Survey Office
Department of Transport"
https://www.nmci.ie/contentfiles/news/1._Irelands_Membership...

I think that's what you should call an "inspector marítimo náutico".