这位政治家就环境问题发表了演讲。

The politician ___delivered ___a ___speech on environmental issues.

然后，他向公众发表了演讲。

Then, he ___delivered ___a ___speech to the public.

她计划在研讨会上发表讲话。

She is scheduled to ___deliver ___a ___talk at the seminar.