What are the hybridizations of the leftmost and rightmost carbon on propyne?
An easy trick to remember is that the number of electron groups around a chosen central atom correspond to the superscripts on the hybrid orbital name that that central atom uses.
You can think of the process of hybridization as the central atom "planning ahead" to prepare for any future bonds it may make (even if they make less than they "plan" for). Any electron groups that are lone pairs can make more bonds. Thus, they all count towards the total number of possible bonds that can be made in the future.
Since the left carbon has four electron groups (what is the electron geometry?), it has
Based on that information, can you predict the hybridization around the righthand carbon? Hint: one triple bond is one electron group, just as one single bond is one electron group.