SUBORDINATION is one of the most important grammatical concepts you will encounter. In order to understand subordination, you need to have a good grasp of unit 5 and unit 7. You also need to get into the habit of looking closely at the meanings of sentences.
The extracts below exhibit a perfectly normal level of subordination for English, but are grammatically quite complex:
The parents of a boy hit on the head by a golf ball were yesterday at his bedside after he underwent surgery. The boy was hit on the temple by the ball which had been struck by a friend in a park near his home at West Wellow, near Romsey, Hampshire.
Glasgow Herald 5/1/91
The sender of the first correct solution opened will receive a gold-plated brown marble lacquered ball-point pen worth over £35 from crossword sponsors Forrest Jewellers.
ibid. 1/11/92