maybe you know the "wake " means there are reason and cause. I would like to know if "wake desu" can only be used after a noun between "to iu" in the Present, like: Generally we use to "~to iu wake desu" ...Sensei to iu wake desu →it means because Sensei. ...Sensei (da) wake desu. →you can not say this sentence. if you want to use like this sentense maybe just ...Sensei desu.→it means because Sensei. The same question but with "wake de wa nai". ...Sensei to iu wake de wa nai →it means because person is not Sensei. ...Sensei (da) to iu wake de wa nai→it means because person is not Sensei. You can use both sentence. this is an apple "kore wa ringo desu" and "kore wa ringo da" there sentence were same meaning. second sentence "da" means ..Sensei (da) to iu wake de wa nai I found a site that when saying "wake ni wa ikanai" after a noun it would be necessary "de iru" after the noun + wake ni wa ikanai. Yes we usual use "de iru wake ni wa ikanai. for example Watasi wa Sensei de iru wake ni wa ikanai.→I can not remain a teacher. Kare ga suki da to kizuita toki kara, mou tada no tomodachi de iru wake ni wa ikanaku natta.→ok Kare ga suki da to kizuita toki kara, mou tada no tomodachi (da) wake ni wa ikanaku natta.→it is not possible.

(da) wa naniwo arawasiteiru tumori desuka? Soreniyotte kotaega kawarimasu.