**Core Concept**
The Dutch cap refers to a barrier method of contraception that involves physically blocking the cervical os to prevent sperm from entering the uterus. This method relies on the cervical mucus and the structure of the cervix to achieve its contraceptive effect.

**Why the Correct Answer is Right**
The Dutch cap, also known as a diaphragm, is a concave rubber or silicone dome that fits over the cervix, creating a physical barrier to sperm entry. It is typically used in conjunction with a spermicide to enhance its effectiveness. The cervical mucus and the shape of the diaphragm work together to prevent sperm from traversing the cervical os and reaching the egg for fertilization.

**Why Each Wrong Option is Incorrect**
**Option A:** The cervical cap is a different type of barrier method that is smaller and more flexible than the diaphragm. It is not the Dutch cap.
**Option B:** The intrauterine device (IUD) is a form of long-acting reversible contraception that is inserted into the uterus, not the cervix. It is not the Dutch cap.
**Option C:** The condom is a barrier method that covers the penis during intercourse, not a device inserted into the cervix. It is not the Dutch cap.

**Clinical Pearl / High-Yield Fact**
The Dutch cap must be fitted by a healthcare provider to ensure a proper seal and to prevent potential complications, such as expulsion or infection.

**Correct Answer: D. Diaphragm**