Individual electrical symbols are provided in this specification as a suggestion for those who do not have an established code.
选项：

A:In this specification，for those who do not have an established code，individual electrical symbols are given as a suggestion.
B:As a suggestion for those who do not have an established code，individual electrical symbols are required in this specification.
C:As a suggestion for those who do not have an established code，individual electrical symbols are gained in this specification.