C Fill in the correct passive form of the verbs in brackets. 15 The Eiffel Tower................ (visit) by about six million people each year. 16 The exhibits in the museum must not ................ (touch). 17 Luckily, the fire............(put out) before anyone got hurt. 18 After receiving all the results, an effective treatment ..................(prescribe). 19 This article ................(already/ translate) into all European languages. 20 The invitation cards ......... (send) last Friday.

Let's fill in the blanks with the correct passive forms of the verbs provided. 15. The Eiffel Tower **is visited** by about six million people each year. *Explanation:* The Eiffel Tower is the object being acted upon (visited), and the sentence describes a general fact, so we use the present simple passive form (is/are + past participle). 16. The exhibits in the museum must not **be touched**. *Explanation:* 'Must not' indicates obligation and since the exhibits are the objects, we need the passive form with 'must.' So, we use 'must be + past participle'. 17. Luckily, the fire **was put out** before anyone got hurt. *Explanation:* The fire is the object, and the event happened in the past, so we use the past simple passive form (was/were + past participle). 18. After receiving all the results, an effective treatment **was prescribed**. *Explanation:* The treatment is the object, and the action of prescribing happened in the past, so we use the past simple passive form (was/were + past participle). 19. This article **has already been translated** into all European languages. *Explanation:* The article is the object, and the translation has already happened and has relevance to the present, so we use the present perfect passive (has/have been + past participle). 20. The invitation cards **were sent** last Friday. *Explanation:* The cards are the object, and the action of sending happened at a specific time in the past, so we use the past simple passive form (was/were + past participle).