"여기가 시청입니까?"
"Is this place the city hall?" (b) is the matching sentence.
You can think of it as 여기(this place) 가(*) 시청(city hall) 입니까? (is it?), where 가 is a subject marker(particle) with no English equivalent.
This is one of the most basic sentences in Korean corresponding to "A is B".
- 아는 것이 힘이다: Knowledge is power. (아는 것: knowing, 힘: power)
- 하늘이 회색이다: The sky is gray. (하늘: sky, 이: subject marker like 가, 회색: gray)
- 나는 학생입니다: I am a student. (나: I, 는: subject/topic marker, 학생: student)
* 입니까 is the question form of 입니다 (is; 이다, 이에요, 예요, 이야 are equivalents of it).