YOU SAID:
This can't be serious
INTO JAPANESE
これは深刻なことではありません
BACK INTO ENGLISH
This is not a serious thing.
INTO JAPANESE
これは深刻なことではありません。
BACK INTO ENGLISH
This is not serious.
INTO JAPANESE
これは深刻ではありません。
BACK INTO ENGLISH
This is not serious.
That didn't even make that much sense in English.