I have started learning Japanese, and I understand (I think) the simple rules around using the が particle but I keep getting stuck as to why there is no が particle being used after the following question words in the sentences below:
なんさいですか why is this not なんさいがですか なんですか why is this not なんがですか どれですか why is this not どれがですか だれですか why is this not だれがですか
Also why is there no particle to mark the topic i.e. in the first sentence why is the topic not what age (then が), as that is the reason for the sentence.
が is used when you start a conversation using a question word and the thing in question comes after. なんさいが たなかさんですか。How old is Tanaka? なにが たなかさんですか。What is Tanaka? And etc. が separates the question word and the thing in question. If the topic has been set by saying something like たんかさんは だれですか。Who is Tanaka. The topic is Tanaka and we don,t need to repeat the topic in Japanese, so everything after we can just say なんさいですか。How old is he/she. どれですか。Which one is he/she etc. When there is no object or thing to separate we don’t need が. I hope this helped.