Read the announcement carefully and answer the following questions.

PUSPITA HIGH SCHOOL ANNOUNCEMENT

For test registration, 4 identical natural color photographs of yourself must be submitted within 30 days of this application. The photos must be on a white background, printed on thin paper, and must not have been retouched. They should be three quarter-frontal profile. The photos must be 4 cm x 6 cm in size. Write (in a pencil) your name, application number, and the date taken, on the back of each submitted photograph. Thank you.

Registration staff

"____ the photos must not have been retouched."

What does the underlined word mean?