俄罗斯领导人希望引入进一步的变革。

The Russian ___leader wants to introduce further changes.

她被选为活动小组的领导者。

She was elected as ___leader of the campaign group.

当我到达那里时，小组领导把我介绍给其他人，他们都很友好。

When I arrived there, the group ___leader introduced me to all the others, and they all were very friendly.