According to the graph, what is the maximum age at which a 4000 Hz sound wave with an intensity of 20 dB would be heard?

55
60
65
70

“other instruments such as gravimeters and magnetometers are also used in the search for petroleum. extracting crude oil normally starts with drilling wells into an underground reservoir. when an oil well has been tapped, a geologist (known on the rig as the "mudlogger") will note its presence. “ this is what i found on google i hope it

True.it is better to buy a washer with a higher efficiency rating

Is there a picture to go along with this

If its history of, then b) because a) implies only present day (now)