Great civil engineers constructed bridges that are helpful to man. ( now active)

2. is active

More emphasis was given to to the advantages than the dis- advantages. (now passive)

3. is active

The result of the observation will be in corporated into our plans. (now passive)

4. not sure – sorry

1. brides that are helpful to man are constructed by great civil engineers. THIS IS ALREADY IN THE PASSIVE VOICE. DO YOU MEAN “BRIDGES”?

FOR INFORMATION REGARDING WHETHER “BRIDES” ARE HELPFUL TO MAN, PLEASE REFER TO THE “MARRIAGE AND DIVORCE” SUBSECTION OF “FAMILY AND RELATIONSHIPS” IN “YAHOO ANSWERS”.

2. they agreed to give more emphasis on the advantages than the disadvantages. TO EMPHASIZE THE ADVANTAGES OVER THE DISADVANTAGES WAS AGREED UPON. (If you are using “they” as an impersonal pronoun, why do you want to use the passive in the first place? It is better to say “place emphasis” than to say “give emphasis”.

3. we will incorporate in our plans the result of the observation. THE RESULT OF THE OBSERVATION WILL BE INCORPORATED INTO OUR PLANS. (You don’t need to use the personal pronoun “we” because you have already used the possessive adjective “our”.

4. the pyramids was designed to show the connection of one point to another. THIS IS ALREADY IN THE PASSIVE. BY THE WAY, “PYRAMIDS” IS A PLURAL, SO YOU SHOULD BE USING THE PLURAL VERB “WERE”.

Think of the passive voice as using the direct object as the subject.

I’m an English teacher, so loving grammar doesn’t make me strange!