Can sound be produced in a vacuum? explain?

In which of the following cases is work being done on an object? question 2 options: pushing against a locked door carrying a box down a corridor pulling a trailer up a hill suspending a heavy weight with a strong chain

The frequencies refer to the sample data collected from a population of interest when performing a hypothesis test comparing two or more population proportions.

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.