N2 — outside your level filter
write + perhaps because
kaku sei ka
perhaps because; maybe it's because — the cause offered only as a guess
寝不足のせいか、今日は全然集中できないんだよね。
nebusoku no sei ka, kyou wa zenzen shuuchuu dekinai n da yo ne.
Maybe it's the lack of sleep, but I just can't concentrate at all today. casual
雨が続いたせいか、今年のトマトは小さい。
ame ga tsuzuita sei ka, kotoshi no tomato wa chiisai.
Perhaps because of the long spell of rain, this year's tomatoes are small. neutral