The balance in Unearned Revenues prior to adjustment was

$ 2 comma 950$2,950.

If the amount still unearned as of the end of the period is

$ 1 comma 900$1,900,

the adjusting entry needed would be to:

A.debit Unearned Service Revenue,

$ 1 comma 900$1,900;

credit Service Revenue,

$ 1 comma 900$1,900.

B.debit Unearned Service Revenue,

$ 1 comma 050$1,050;

credit Service Revenue,

$ 1 comma 050$1,050.

C.debit Service Revenue,

$ 1 comma 050$1,050;

credit Unearned Service Revenue,

$ 1 comma 050$1,050.

D.debit Cash,

$ 2 comma 950$2,950;

credit Unearned Service Revenue,

$ 2 comma 950$2,950.