In the late 1800's meaning 1870 and after most cities in Europe had Horse-drawn streetcars. Around 1890 electric streetcars began replacing the horse powered ones.
It's similar in the US, but there things developed a little earlyer
Railroads
The train.
It is the nucleus. Mass of electrons is too small
pipeline
Osteoarthritis is the most common form of arthritis in the knees. Having arthritis in the knees is a very common occurrence that can be treated with varying therapies and medications.
Probably the Discobolus.
It's thermal energy my dear.
The most common form of mass transit in the late 1800s was the train. Although there were some horse-drawn vehicles that carried multiple people, trains had by far the bulk of the mass transit population.
People and goods
MTR (Mass Transit Railway)
Carbon-12 is the most common form of Carbon and therefore, counts for most of the atomic mass.
a mudflow
Probably stellar mass black holes
a mudflow
most common type of mass movement is "Landslide"
The atomic mass of the most common form of hydrogen is 1. There are isotopes of hydrogen with a mass of 2 (deuterium) and 3 (tritium), but they are rare.
An avalanche.
The most common way to circumnavigate the continent is aboard a ship. The most common mode of transit on the continent is on foot.
Television is the most widely used form of mass media.