A much-hyped rescue on Chicago Fire and the season finales of The Amazing Race and Survivor are intended to get viewers to tune in. Broadcasters use the viewership numbers collected during four annual periods to set advertising rates for the rest of the year. In other words, commonly co-occur when networks are trying to make themselves look attractive to advertisers.

Sweeps

Explanation:

Sweeps are type of recording that occurs in certain time periods of months for collecting information about viewers habit of start watching television or listening radio , stop watching television or radio time, watched program information , channel numbers etc.  

According to the question sweeps tend to be present when viewership numbers are gathered for annual period for the year for setting advertising rates.This helps in attaining analysis and making advertiser attracted towards that certain network.  

the answer is: c. c.it limited the president’s power to start wars.

the war powers resolution of 1973 requires the president to notify the congress whenever the president wanted to order a military operation to other countries within 48 hours. if after being reviewed the congress disagree with the proposal, that the president will be banned from ordering the operation.

question - in 1827, john walker, a druggist in a small english town, tipped a splint with sulphur, chlorate of potash, and sulphid of antimony, and rubbed it on sandpaper, and it burst into flame. the druggist had discovered the first friction-chemical match, the kind we use to-day. it is called friction-chemical because it is made by mixing certain chemicals together and rubbing them. although walker's match did not require the bottle of acid, nevertheless it was not a good one. it could be lighted only by hard rubbing, and it sputtered and threw fire in all directions. in a few years, however, phosphorus was substituted on the tip for antimony, and the change worked wonders. the match could now be lighted with very little rubbing, and it was no longer necessary to have sandpaper upon which to rub it. it would ignite when rubbed on any dry surface, and there was no longer any sputtering. this was the phosphorus match, the match with which we are so familiar. according the paragraph what was the benefit of the new phosphorus match? it burst into flame when rubbed on sandpaper. it was made by mixing chemicals. it could be ignited on any dry surface. it threw fire in all directions.

answer - matches required natural chemicals