Answer:
The teacher told the students to cover up.
Step-by-step explanation:
Changing a speech from the direct to the indirect form requires certain alternations. Some of these changes include the removal of the speech marks or quotation marks that are in the direct speech and also the change of tenses as and when necessary. Moreover, certain words such as "yesterday" will be changed to the day before, "now" changed to "then" etc. And the indirect speech usually used "told/asked/said" in its reporting form.
The given sentence
"Cover up" the teacher says to the students
will be changed to the indirect form as below-
The teacher told the students to cover up.