The correct answer is Option (4) -Calotropis

In the context of plants, herbivores are their primary predators. Approximately 25 percent of all insects are classified as phytophagous, meaning they feed on plant sap and various plant parts. Unlike animals, plants cannot escape from their predators, so they have evolved a remarkable array of both morphological and chemical defenses to protect themselves from herbivores.

One of the most common morphological defenses in plants is the presence of thorns, exemplified by species like Acacia and Cactus. Additionally, many plants have developed the ability to produce and store chemicals that have adverse effects on herbivores when ingested. These chemicals can make the herbivore sick, inhibit its feeding or digestion, disrupt its reproduction, or even lead to its death. For instance, Calotropis, a weed found in abandoned fields, produces highly toxic cardiac glycosides, which deter grazing animals such as cattle and goats from consuming it.

Interestingly, several chemical substances that we extract from plants on a commercial scale, such as nicotine, caffeine, quinine, strychnine, and opium, are actually produced by plants as defenses against herbivores and browsers. These chemical defenses play a crucial role in protecting plants from being consumed by their herbivorous predators.