Which sentence does not have awkward sentence structure? When the judge entered the courtroom, everyone stood up and waits for him to be seated.
When the judge entered the courtroom, everyone stands up and waited for him to be seated.
When the judge entered the courtroom, everyone stood up and waited for him to be seated.
None of the above sentences has a correct sentence structure,

right angles are formed by perpendicular lines. if the lines would extend, to make two intersecting lines, they would form four right angles.

what is the context here? we need to know what story you're talking about : )

onto a large boat, and mark the water level that the boat sinks to. then, take the elephant out and put a bunch of marked weights onto the boat until it reaches the same water level. add up the masses of the weights to get the weight of the elephant.