Match the columns.

Column-A (Class)	Column-B (Common name)
i. Chlorophyceae	a. Brown algae
ii. Phaeophyceae	b. Green algae
iii. Rhodophyceae	c. Blue-green algae
iv. Cyanophyceae	d. Red algae

The correct answer is i-b, ii-a, iii-d, iv-c.

This question asks us to match each algae class (Column-A) with its correct common name (Column-B). Let's analyze each class name carefully — the names themselves contain etymological clues that reveal their common names.

Step 1: Decode each class name using its Greek/Latin root.

i. Chlorophyceae → b. Green algae
The prefix "Chloro-" comes from the Greek word chloros, meaning green. These algae are rich in chlorophyll-a and chlorophyll-b, giving them a distinct green color. Examples include Spirogyra, Chlamydomonas, and Ulva. Hence, Chlorophyceae = Green algae.

ii. Phaeophyceae → a. Brown algae
The prefix "Phaeo-" comes from the Greek word phaios, meaning brown/dusky. These algae contain the pigment fucoxanthin, which gives them a characteristic brown color. They are mostly marine. Examples include Fucus, Laminaria, and Sargassum. Hence, Phaeophyceae = Brown algae.

iii. Rhodophyceae → d. Red algae
The prefix "Rhodo-" comes from the Greek word rhodon, meaning rose/red. These algae contain the pigment phycoerythrin, which gives them a red color. They are predominantly marine. Examples include Polysiphonia and Porphyra. Hence, Rhodophyceae = Red algae.

iv. Cyanophyceae → c. Blue-green algae
The prefix "Cyano-" comes from the Greek word kyanos, meaning blue. These are actually prokaryotic organisms (classified under Kingdom Monera/Bacteria today) containing the pigment phycocyanin, giving them a blue-green appearance. Examples include Nostoc, Anabaena, and Oscillatoria. Hence, Cyanophyceae = Blue-green algae.

Step 2: Compile the correct matches.

Therefore, the correct match is: i-b, ii-a, iii-d, iv-c.