Q5. that を a と聞き間違え。よく聞いたら確かにthatでした。
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Facebookディクテーションテスト2013年04月23日(火)版(No.686) - 結果
http://www.facebook.com/gogakuru?sk=app_221243961236240
Q1 Do you sell sunscreens here?
○ Do you sell sunscreens here?
/english/phrase/5034
Q2 I'll be counting on you.
○ I'll be counting on you.
/english/phrase/1873
Q3 Do you mean twelve in all?
○ Do you mean twelve in all?
/english/phrase/582
Q4 Don't lose heart till the last minute.
○ Don't lose heart till the last minute.
/english/phrase/22343
Q5 A benefit of membership is that purchases are discounted.
× A benefit of membership is a purchases at discounted.
/english/phrase/23154