Final answer:
In Vivaldi's "Winter", the technique that creates a harsher tone by playing near the bridge is called sul ponticello.
Step-by-step explanation:
In Antonio Vivaldi's "Winter" from The Four Seasons, the technique where the players keep the bow very close to the bridge to create a harsher, more metallic sound, is called sul ponticello. This technique contrasts with other methods such as pizzicato, where the strings are plucked with the fingers, and col legno, where the wood of the bow is used to strike the strings. The answer to the question is a. Sul ponticello.