Answer:
1. correct
2. correct
3. Ich habe viel gearbeitet. (D, not C)
The past participle gearbeitet should be placed at the end.
4. Ich habe in der Bibliothek gelernt. (C, not B)
The past participle of the verb lernen is gelernt. You need to add the prefix ge- and the suffix -t to the verb root because it is a weak, or regular, verb. (The verb lernen consists of the root lern- and the infinitive ending -en.)
5. Wir haben sie natürlich gelesen. (A, not B)
Lesen is a strong, or irregular, verb, so its past participle form is also irregular: gelesen.
6. correct
7. Wir haben "Herr der Ringe" gesehen. (D, not B)
Sehen is a strong, or irregular, verb, so its past participle form is also irregular: gesehen.
8. Ich habe ihm eine neue Uhr geschenkt. (A, not C)
The past participle of the verb schenken is geschenkt. You need to add the prefix ge- and the suffix -t to the verb root because it is a weak, or regular, verb. (The verb schenken consists of the root schenk- and the infinitive ending -en.)
