Active voice versus passive voice：练习题

Change the following active sentence into the passive voice:
"The janitor cleaned all the windows yesterday."

Convert the following sentence into the passive voice:
"The principal will deliver a speech during the assembly tomorrow."

Identify the correct passive form of the sentence below, paying close attention to the modal verb:
"The management must take the employees' concerns into account."

Identify the correct passive form of the following sentence:
"The teacher gave the students several brochures for the reading task."

Identify the correct passive version of this sentence where the subject is unknown:
"Someone has stolen the prototype from the lab."

In scientific reports, we often describe the outcome of an experiment using the passive voice. Rewrite the following sentence using the passive voice:
"The scientist observed bubbles on the surface of the eggshell."

Based on the study of egg components, rewrite this sentence into the passive voice, keeping the same meaning:
"Calcium carbonate forms the majority of the eggshell structure."

Identify the grammatical error in the passive transformation of the following sentence and provide the correct version:
Active: "The curriculum reform has placed emphasis on motivating students."
Incorrect Passive: "Emphasis have been placed on motivating students by the curriculum reform."

Rewrite the following active voice sentences into the passive voice. Be sure to keep the same tense and include the agent with 'by' where appropriate.

a) The chef is preparing a delicious five-course meal.
b) The scientist has discovered a new species of butterfly.
c) The volunteers will plant fifty trees in the park tomorrow.

Compare the two sentences below taken from a scientific procedure:
Sentence A: "The technician poured 50ml of vinegar into the beaker."
Sentence B: "50ml of vinegar was poured into the beaker."

(a) Identify which sentence is in the active voice and which is in the passive voice.
(b) Explain why Sentence B is generally preferred over Sentence A in scientific report writing.