English F. Pronouns: Interrogative, Relative, Demonstrative, Indefinite

What is the longest river in the United States?
what, interrogative
The Missouri, which flows 2,540 miles, is the longest river.
which, demonstrative
In fact, the Missouri is one of the longest rivers in the world.
one, indefinite
How many of the world's rivers are longer than the Missouri?
how, interrogative
The Ohio River and the Missouri River, which are tributaries of the Mississippi River, flow in the Mississippi at Cairo, Illinois, and St. Louis, Missouri.
which, demonstrative
Both are vital transportation routes.
both, demonstrative
These, along with other smaller rivers, help make up the Mississippi River Basin.
these, demonstrative
Statistics show that the Mississippi River carries almost two thirds of the country's inland freight.
that, demonstrative
St. Louis, Memphis, and New Orleans are several of the cities on the river.
several, indefinite
Which is the largest state bordering the Mississippi River?
which, interrogative
A famous writer who is associated with the Mississippi is Mark Twain.
who, relative
Twain wrote about whatever was around his hometown of Hannibal, Missouri.
whatever, relative
The bustling life of the river was something Twain described in book after book.
something, indefinite
Nothing was closer to the writer's heart.
nothing, indefinite
Three books that are set on the river are Life on the Mississippi, Tom Sawyer, and Pudd'nhead Wilson
that, demonstrative