Which of the following statements is correct when describing the forces at work on a bridge a. wires are in tension b. large posts are in compression c. the bridge deck is both in tension and in compression

All the statements are true

Explanation:

A) Wires are in tension.

It is true because the loads exerted on the bridge are taken by each of the cables of the bridge. these cables transmit the force to the pillars or columns of the bridge. (check the image 01)

B) Large posts are in compression.

It is true each of the loads of the cables is tension, are transmitted to the columns of the bridge, in this way the balance will be maintained (check the image 01)

C) The bridge deck is both in tension and compression.

Yes it is true, the superior part of the deck will be in compression and the inferior part will be in tension, this can be seen in the image 02

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.