A The batteries are series-aiding and the total source voltage equals 21 V.

B The batteries are series-opposing and the total source voltage equals 3 V.

C The batteries are series-aiding and the total source voltage equals 3 V.

D    <div class="bix-td-option" id="tdOptionNo_D_130"><span id="lnkOptionLink_D_130" class="mdi mdi-alpha-d-circle-outline"></span></div>
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                                                        <div class="flex-wrap">The batteries are <b><i>series-opposing</i></b> and the total source voltage equals 21 V.</div>
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