What is the cause of Apache startup error?

Question

Apache HTTP Server

Starting httpd: Syntax error on line 89 of /etc/httpd/conf/httpd.conf:
Invalid command 'IncludeOptional', perhaps misspelled or defined by a module not included in the server configuration

The code itself
IncludeOptional conf.d/*.conf

Answer 1

Apparently Apache doesn't support the IncludeOptional directive.
She appeared in version 2.4

Answer 2

You apparently have an old opach, use the usual include