15) On its many woody branches, the jojoba produces a fruit that is 40 per cent to 60 percent liquid wax.

 (16) This liquid substance, called jojoba oil, is valuable.

 (17) It can be used as a base for all kinds of cosmetics. 

(18) It works well as an ingredient in high-quality machine oils. 

(19) By domesticating the jojoba, scientists hope to change unproductive desert land into productive agricultural land.

Question 7: Read the five sentences above (15-19) and find the common elements in these sentences.