A wedding results in a joining, or a marriage, so choice d is the essential element. Love (choice a) usually precedes a wedding, but it is not essential. A wedding may take place anywhere, so a church (choice b) is not required. A ring
(choice c) is often used in a wedding, but it is not necessary.

An agreement is necessary to have a contract. A contract may appear on a document (choice b), but it is not required. A contract may be oral as
well as written, so choice c is not essential. A contract can be made without an attorney (choice d).

A directory is a listing of names or hings, so choice b is the essential element. A telephone (choice a) often has a directory associated with it, but it is not essential. A computer (choice c) uses a directory format to list files, but it is not required.Names (choice d) are often listed in a directory, but many other things are listed in directories, so this is not the essential element.

A faculty consists of a group of teachers and cannot exist without them. The faculty may work in buildings (choice a), but the buildings aren't essential. They may use textbooks (choice b) and attend meetings (choice d), but these aren't essential either.

A cage is meant to keep something surrounded, so enclosure is the essential element. A prisoner (choice b) or an animal (choice c) are two things that may be kept in cages, among many other things. A zoo (choice d) is only one place that has cages.

A saddle is something one uses to sit on an animal, so it must have a seat (choice b). A saddle is often used on a horse (choice a), but it may be used on other animals. Stirrups (choice c) are often found on a saddle but may not be used. A horn (choice d) is found on Western saddles, but not English saddles, so it is not the
essential element here.

Something cannot vibrate without creating
motion, so motion is essential to vibration.

Without a first-place win, there is no champion, so winning is essential. There may be champions in running, swimming, or speaking, but there are also champions in many other areas.

The essential part of a cell is its nucleus.Not all cells produce chlorophyll (choice a). Not all cells are nerve cells (choice c). All living things, not just humans (choice d), have cells.

A glacier is a large mass of ice and cannot exist without it. A glacier can move down a mountain, but it can also move across a valley or a plain, which rules out choice a. Glaciers exist in all seasons, which rules out choice b. There are many glaciers in the world today, which rules out choice c.