Enzymes catalysing a transfer of a group, other than hydrogen is placed in group

Why hydrogen is placed in group I?

Which of the following group of enzymes helps in catalysing a transfer of a group (other than hydrogen) between a pair of substrates ?

Which of the following group of enzymes helps in catalysing a transfer of a group (other than hydrogen) between a pair of substrates ?

Enzymes catalysing transfer of any chemical group except hydrogen are included

Why hydrogen should be placed in group I ?

Why hydrogen should be placed in group I ?

Enzymes catalysing removal of group and formation of double bond are

Enzyme catalysing removal of groups and formation of double bond are