There are a couple of Traditional Chinese characters in the above lessons that need to be explained.
In traditional form there exist two characters: 隻 (zhī) and 只(zhǐ). The former is the measure word for animals while the latter means “only.” In the simplified form both these meanings are combined into 只 with the meaning and pronunciation derived from context.
Similarly, the traditional form distinguishes between 它 (tā) and 牠 (tā) with the former referring to objects while the latter refers to animals. In the simplified form, both are combined using the character 它.
The traditional Chinese vocabulary for lessons 44 and 45 has since been updated to reflect the above.