Take a look at the sentence again:
Jacob's physics notes were tucked in his book bag. A half-read copy of
Moby-Dick served as a coaster for a glass of cold soda. An unopened
trigonometry book was __________ on the desk. Although final exams were
only two days away, Jacob decided to play another level of Tomb Raider,
his favorite computer game.
The trigonometry book is resting on the desk. Thus, you need a form of lie. Since the sentence has a progressive verb, you need the present participle. Consult the table below or review the rules.
| Infinitive | Definition | Simple Present | Simple Past | Past Participle | Present Participle |
| to lay | to put something down | lay(s) | laid | laid | laying |
| to lie | to rest or recline | lie(s) | lay | lain | lying |