The short-run aggregate supply curve (AS) is upward sloping because:

an increase in the aggregate price level will cause an increase in the interest rate and a reduction in output.
a reduction in the aggregate price level causes a reduction in nominal money demand and a reduction in the interest rate.
an increase in the nominal wage causes a reduction in the amount of output that firms are willing to produce.
an increase in output causes an increase in employment, a reduction in unemployment, an increase in the nominal wage and an increase in the price level.

When the price level is equal to the expected price level, we know from our theory that:

everyone who wants a job is working.
the goods market is in equilibrium.
the unemployment rate is equal to the natural rate of unemployment.
both the price level and the expected price level are equal to one.
financial markets are in equilibrium.

The natural level of employment will increase when which of the following occurs?

an increase in the markup of prices over costs
an increase in unemployment benefits
an increase in the actual unemployment rate
all of the above
none of the above