Three sentences are given. You need to find if they are grammatically correct or incorrect and mark the answer accordingly.

(P)  At the end of the book, readers were invited to help study butterfly migrations.

(Q) They were asked to tag butterflies for research by Dr. Frederick A. Urquhart of University of Toronto, Canada.

(R)  Ebright’s mother written to Dr. Urquhart, and soon Ebright was attaching light adhesive tags to the wings of monarchs