A friend of mine asked me a question today if D is multiplatform I particularly believe it is but I wanted to know the opinion of who has already developed the most time in it and even of the developers because I looked for some cisa on the net about such subject and did not find anything that said about Whether or not it is multplataforma ..
For C and C ++ if I develop in a standard ansi then could compile on both Unix, Linux, Windows platforms with D does this happen?

Yes, D works on the major desktop platforms easily. There isn't an ANSI standard but there's just one D language.