Haha, that's a funny joke. RAC is not a language (it's a clustered database) and it's *certainly* not easy.
The language you already know is most likely the easiest. If you know C, use that; if Java, use that. But it depends what you mean by "easy", because the other part of the equation is the API you use (application programming interface), of which there are several.
OCI provides the most power for using Oracle. You can do everything through OCI. "Can I...?" is always Yes. However that means it is necessarily quite complicated and so not easy, but it is complete.
The precompiler languages Pro*C/C++, Pro*Cobol, Pro*Fortran etc were designed to be easy-ish; you can do most of the things you can with OCI, but they have their limitations and quirks. "Can I...?" will sometimes be No, but in those times you can fall back to OCI.
ODBC is a portable API, designed by Microsoft to increase market penetration of SQL*Server, and it's supposed to give a single interface that will work with any database. However different DBs work differently, and different implementations of the ODBC driver for the same DB work differently as well, so the same code written for the Microsoft ODBC driver for Oracle won't necessarily work in the same way as the Oracle ODBC driver for Oracle, and that same code won't necessarily work with any ODBC driver for DB2. But ODBC was designed to be used by several different Microsoft languages and will work with Visual Basic, and this is possibly the "easiest" way to write Oracle programs.