it and this / theme and rheme

Examine the following text and complete the following rule below.

The Alexander Technique can be an expensive hobby to learn. This causes many people to give up before they have enjoyed its benefits. Studying AT takes time. It also requires patience. This makes it an unsuitable hobby for today’s younger generation who want everything now!

The so-called Alexander Position is excellent therapy for the back. It allows for the replacement of fluid between the vertebrae in the spine. This effectively makes people slightly taller by a few millimetres. In the long term it can help to prevent injury and back pain caused by years of bad posture.

Alexander Technique also helps to prevent injury when performing repetitive tasks. This is especially useful for musicians, who have to hold their instruments in unnatural positions for long periods of time. Projecting the head forward while keeping the neck free is also important for singers. It helps them to make their voices louder, and this is important for opera singers who sing without electronic amplification.

it is generally used to refer back to ¹
this is generally used to refer back to ²
it and this both behave as ³

In the following two paragraphs, circle it or this as appropriate.

The head-neck-back relationship is an important part if Alexander Technique. In children ⁴ remains the same when the child is sitting or standing, whereas in adults ⁵ changes as the adult moves from a standing to a sitting position. Alexander hypothesised that ⁶ might cause back problems in adult humans.

Another important feature of Alexander Technique is inhibition. ⁷ is the attempt to 'forget' bad use of the body before exercising 'correct' use. ⁸ involves, for example, telling yourself to ‘not stand’ before standing. Not surprisingly, ⁹ is usually quite confusing for Alexander Technique beginners!