Read each pattern and its example, then write your own sentence on the line.
〜せいか plain + せいか（N + のせいか、na-adj + なせいか）
Offers a tentative reason for something, usually mildly negative: perhaps because of A, B happened. Softer and less certain than 〜せいで. Everyday register.
寝不足のせいか、今日は集中できない。 Perhaps because I didn't sleep enough, I can't concentrate today.
〜につき N + につき（理由、または単位「〜ごとに」）
Formal 'due to' in notices and signs, and also 'per' with counters. Stiff written style: you see it on shop signs and official announcements, not in casual talk.
本日は改装中につき、休業させていただきます。 As we are undergoing renovation today, we will be closed.
〜ようとする V-volitional（〜よう／〜おう）+ とする
Shows an attempt to do something, or the moment just before an action starts. In the negative (〜ようとしない) it means someone stubbornly refuses. Neutral register.
電車に乗ろうとしたとき、ドアが閉まってしまった。 Just as I was about to board the train, the doors closed.
〜まい / 〜まいか V-dict + まい（II類は V-stem + まい も可、する→すまい）
Literary negative: firm resolve ('I will never...') or conjecture ('probably not'). Stiff and old-fashioned, mainly in writing, speeches and set phrases like ではあるまいか.
あんな店には二度と行くまい。 I will never go to a shop like that again.
〜べきではない V-dict + べきではない（する→すべきではない も可）
A strong judgment that something is wrong and must not be done. Heavier and more moral than 〜ないほうがいい; used in advice, rules and opinion writing.
感情的になって相手を責めるべきではない。 You shouldn't get emotional and blame the other person.
〜ないことには V-ない ／ i-adjくない ／ Nでない + ことには（後は否定）
Unless the first thing is done, the second is impossible or cannot be known. The main clause is always negative. Neutral register, common in explanation and discussion.
実際に見てみないことには、判断できない。 I can't make a judgment unless I actually see it.