Hello, jahanifar - and welcome to English Forums. we put s to last latter of verb in simple present tense -- for the 3rd person singular only: He/She it runs . -- Yes, the singular form of the verb.
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jahanifarA)"Infulanza cause pain and fever." or "Infulanza causes pain and fever." (infulanza = it ??)
B)"Mathematics create problems for many students, but not for me!" or
"Mathematics creates problems for many students, bur not for me! ( Mathematics = it ??)
jahanifarThose Examples are on G7's page at grammar booster.All six appear to be singular, although audibly the last five seem to end with an "s" sound.