You observe a yield curve and notice that its slope is negative. Would you call this a 'normal' yield curve? Why?

a$.$ Yes, yield curves have a negative slope in all market circumstances.

b$.$ Yes, yield curves have a negative slope in normal market circumstances.

c$.$ No$,$ yield curves tend to have positive slopes in 'normal' markets.

d$.$ No$,$ yield curves tend to be flat in 'normal' markets.