We should appreciate that the telephone here have been working as
efficient in the past. The bolded part is the error in the sentence.
An adjective is used to describe a noun and usually has a suffix of -ly . In this
case, the noun is the telephone which is being described as being efficient
which should be efficiently instead.
Other examples of adjectives include hurriedly, hastily etc which is why 'as
efficient' is the most appropriate choice.
Read more about Adjectives here https://brainly.com/question/24570768
