25. From what stage musical does the song which Tom Lehrer adapted for "A Litre and a Gram" come?
From Quiz The Physical Revue Featuring Tom Lehrer
Answer: 
Guys and Dolls
The tune is that of "A Bushel and a Peck", by Frank Loesser, from the show "Guys and Dolls".  As the first verse tells us, 
"I love you, a liter and a gram
A liter and a gram, and it's crazy that I am,
A meter and a yard, and a Newton and a Watt,
A Newton and a Watt, and I wanna know a lot about you,
about you."
A liter (or litre) is a metric unit of volume, while the gram is a metric unit of mass.  The rest of the song includes reference to many different common units used in making physical measurements, both metric and Imperial - poundal, dyne, foot-pound, erg, joule, calorie, centigrade, Fahrenheit.