Due to frequent changes in, or varying combinations of, some types of equipment such as avionics and instrumentation, one or more separate documents for these products may be required.
选项：

A:One or more separate documents for some types of equipment such as avionics and instrumentation may be required because they change frequently or they have various combinations.
B:Some types of equipment such as avionics and instrumentation are changed regularly or combined in different forms, requiring to have one or more separate documents.
C:Some types of equipment such as avionics and instrumentation are often revised or combined differently to require one or more separate documents.
D:1922