The correct option is (a).
Explanation
Blood is a specialized fluid connective tissue responsible for the transport of nutrients, gases, and waste products throughout the body. Structurally, it consists of a fluid matrix known as plasma and formed elements (erythrocytes, leukocytes, and platelets).
Statement-wise Analysis:
- Statement 1 is Correct: Blood is classified as a connective tissue because it connects various body systems and possesses a matrix. Like other connective tissues, it is derived from the mesoderm.
- Statement 2 is Incorrect: The matrix of blood is fluid and is called plasma. It is not rigid. A rigid, solid matrix is characteristic of bone tissue (which contains calcium salts and collagen fibres). Bone marrow is the hematopoietic tissue located within the cavities of bones, not the matrix of the blood itself.
- Statement 3 is Incorrect: Plasma constitutes approximately 55% of blood and is not devoid of proteins or salts. It contains:
- Proteins: Fibrinogen (for clotting), globulins (for defense mechanisms), and albumins (for osmotic balance).
- Salts/Minerals: Ions such as sodium ($Na^+$), calcium ($Ca^{++}$), magnesium ($Mg^{++}$), and bicarbonate ($HCO_3^-$).
Key Takeaway:
Blood is a fluid connective tissue characterized by a liquid matrix called plasma, which contains essential proteins and salts, distinct from the rigid matrix found in bone tissue.