1. The answer is b.) whom.
2. The answer is b.) sudden.
Answer:
All of the people at this conference are _____________.
A. Mathematic teachers
B. Mathematics teacher
C. Mathematics teachers ✔
D. Mathematics’ teacher
E. Mathematic’s teachers
Explanation:
Mathematics = a subject; long for 'maths'
Teachers = plural of teacher; since it's describing all the people we'll use the plural form.