How is search done in #include and #include somelibrary.h normally or conventionally?

• A. When former is used, current directory is searched and when latter is used, standard directory is searched
• B. When former is used, predefined directory is searched and when latter is used, current directory is searched and then predefined directories are searched
• C. When former is used, search is done in implementation defined manner and latter is used to search current directory
• D. For both, search for somelibrary is done in implementation-defined manner