To what recent news item does this cartoon refer?
a) Democratic presidential candidates Joe Biden, 77 and Bernie Sanders, 78, like to ride motorized scooters around their campaign stops
b) both Biden and Sanders vowed this week, if elected, to give every American a free electric scooter as a way to combat climate change
c) Bernie Sanders challenged rival Joe Biden to a scooter race after Biden challenged Bernie to a push up contest
d) a new poll shows Sen. Bernie Sanders rising in the national Democratic race for president, joining former VP Joe Biden in a two-person top tier above the rest of the field