Step 1: Understanding cardiac glycosides.
Cardiac glycosides are toxic compounds that affect the heart by altering cardiac muscle contractions.
Step 2: Source plants.
Calotropis (milkweed) produces poisonous cardiac glycosides, which are harmful if ingested.
Step 3: Analyzing options.
(A) Cactus: Incorrect — No cardiac glycosides.
(B) Calotropis: Correct — Produces toxic glycosides.
(C) Coffee plant: Incorrect — Contains caffeine, not glycosides.
(D) Tobacco: Incorrect — Contains nicotine, not glycosides.
Step 4: Conclusion.
Thus, Calotropis is the plant producing cardiac glycosides.