**Core Concept**
Radium is a radioactive element that undergoes alpha (α), beta (β), and gamma (γ) decay, releasing various forms of radiation. This process is a fundamental concept in nuclear physics and radiology, where understanding the different types of radiation emitted is crucial for safe handling and application of radioactive materials.

**Why the Correct Answer is Right**
Radium-226, a common isotope of radium, decays into radon-222 through alpha decay, releasing an alpha particle (helium nucleus). Subsequently, radon-222 decays through beta decay, emitting a beta particle (electron or positron). Additionally, radon-222 and other radium isotopes can undergo gamma decay, releasing gamma radiation, which is high-energy electromagnetic radiation. This sequence of decays is a characteristic feature of radium's radioactive properties.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because radium does not emit neutrons as a primary mode of decay. Neutron emission is a characteristic of certain nuclear reactions, but it is not a typical decay mode for radium.

**Option C:** This option is incorrect because radium's decay sequence involves beta decay, which is not mentioned in this option. Beta decay is a critical component of radium's radioactive behavior.

**Option D:** This option is incorrect because radium does not primarily emit neutrons. While neutron emission can occur in certain nuclear reactions, it is not a characteristic feature of radium's decay.

**Clinical Pearl / High-Yield Fact**
When working with radioactive materials, it is essential to understand the different types of radiation they emit. Alpha particles can be stopped by a sheet of paper, while beta particles require a thicker barrier, such as a few millimeters of metal. Gamma radiation, however, requires thick, dense materials like lead to effectively block it.

**✓ Correct Answer: B. a, b, g**