Which period is the shortest in the long form of the periodic table? Name all the
elements in this period.

The first period is the shortest in the long form of periodic table

Explanation:

the long form or the modern periodic table is based on ht modern periodic law. it has 7 periods and 18 groups. this periodic table is widely used by people all over the world. the chemical and physical properties of the elements can be easily identified due to their classification into groups and periods or their position in the periodic table. the first period is the shortest in the long form of periodic table. there are two elements present, they are- hydrogen(H) and helium (He)

the answer is b & c i believe : )