Sister chromatids are attached to each other at an area called the a. centriole. b. centromere. c. spindle. d. chromosomes.

Step 1: Define the Problem

Identify the area where sister chromatids are attached to each other.

Step 2: Break Down the Problem

• Understand the structure of chromosomes and the role of sister chromatids.
• Identify the specific part of the chromosome where the attachment occurs.

Step 3: Apply Relevant Concepts

• Sister chromatids are identical copies of a chromosome connected together.
• The centromere is the region where these chromatids are most tightly connected.

Step 4: Analysis, Verify and Summarize

• Analyze the options provided:
  • a. Centriole: Involved in cell division but not in attaching chromatids.
  • b. Centromere: The correct region where sister chromatids are attached.
  • c. Spindle: Refers to spindle fibers involved in chromosome movement.
  • d. Chromosomes: The entire structure, not the specific attachment point.

Final Answer

b. centromere.