Common Components in Fluids and Tissues Steps:

• Identify the question: Determine elements present across blood vessels (containing blood), lymph (lymphatic fluid), and tissue (interstitial fluid).
• Recall key components: Blood includes plasma (water, proteins, electrolytes), cells (RBCs, WBCs, platelets); lymph has WBCs, proteins, water but no RBCs; tissue fluid has water, proteins, electrolytes, some WBCs.
• Compare overlaps: Common to all are water, dissolved proteins, and electrolytes; specific cells like RBCs are absent in lymph/tissue.
• Match to options: Assuming 1=water, 2=proteins, 3=RBCs, 4=electrolytes, select those universally present.

Why A is correct:

• Option A (1,2,4) includes water, proteins, and electrolytes, which are foundational in plasma, lymph, and interstitial fluid per fluid composition definitions.

Why the others are wrong:

• B includes 3 (likely RBCs), absent in lymph and tissue.
• C omits 2 and 4, excluding key proteins and electrolytes.
• D omits 1, ignoring water as the primary solvent.

Not enough information to confirm exact labels for 1-4.

Final answer: A