The suffix that means abnormal reduction in number isSelect one:a.-algia.b.-penia.c.-sclerosis.d.-apharesis.

Break Down the Problem

1. Identify the meanings of each suffix to determine which one refers to "abnormal reduction in number."
2. Assess which option aligns with the medical definition for reduction.

Relevant Concepts

• -algia: usually refers to pain.
• -penia: typically denotes a deficiency or reduction in number.
• -sclerosis: refers to hardening of tissue.
• -apharesis: refers to a process of removing or taking away.

Analysis and Detail

1. The key phrase is "abnormal reduction in number."
2. Reviewing each suffix:
   • -algia doesn't pertain to reduction.
   • -penia is commonly used in medical terminology to denote a decrease, such as in "leukopenia" (low white blood cell count).
   • -sclerosis indicates hardening rather than reduction.
   • -apharesis involves removal but not specifically a reduction in number.

Verify and Summarize

Upon comparison, -penia clearly stands out as the suffix that signifies an abnormal decrease in quantity.

Final Answer

The correct suffix that means abnormal reduction in number is b. -penia.