Question

a sforzando is...
a sudden, strong accent
sing/play the note louder with special emphasis
smooth and connected
hold the note longer than its normal value

Explanation:

Sforzando (sf or sfz) is a dynamic marking in music that indicates a sudden, strong accent on a single note or chord. The other options describe different musical techniques: the blue card describes a general accent/emphasis (not specific to the sudden, sharp nature of sforzando), the orange card describes legato, and the teal card describes a tenuto or hold.

Answer:

A sudden, strong accent