Passage (Charles Darwin, *On the Origin of Species*, 1859, Ch. III): "I should premise that I use the term Struggle for Existence in a large and metaphorical sense, including dependence of one being on another, and including (which is more important) not only the life of the individual, but success in leaving progeny. Two canine animals in a time of dearth, may be truly said to struggle with each other which shall get food and live. But a plant on the edge of a desert is said to struggle for life against the drought, though more properly it should be said to be dependent on the moisture. A plant which annually produces a thousand seeds, of which on an average only one comes to maturity, may be more truly said to struggle with the plants of the same and other kinds which already clothe the ground. The missletoe is dependent on the apple and a few other trees, but can only in a far-fetched sense be said to struggle with these trees, for if too many of these parasites grow on the same tree, it will languish and die. But several seedling missletoes, growing close together on the same branch, may more truly be said to struggle with each other." The four examples Darwin presents (canines, desert plant, seed plant, and mistletoe) are best understood as:

The four examples are ordered along a spectrum: 1. **Canines in dearth** — "may be **truly** said to struggle." Most literal. 2. **Plant on desert edge** — "said to struggle for life against the drought, though **more properly** it should be said to be dependent on the moisture." One step less literal — drought is not an adversary in the usual sense. 3. **Plant producing a thousand seeds** — "**more truly** said to struggle with the plants of the same and other kinds." A subtler form: competition for ground without direct contact. 4. **Mistletoe** — "only in a **far-fetched** sense be said to struggle with these trees." Most metaphorical. Darwin's qualifying language (truly → more properly → more truly → far-fetched) tracks the move along the spectrum. The structural point is that *Struggle for Existence* is an umbrella term whose extension shades from literal competition to dependency, and the four examples lay out that gradient. - **A** misses the spectrum — Darwin is explicit that the cases are *not* equally literal. - **C** is unsupported: the examples include plants and mistletoe (non-vertebrates), so the point cannot be to *restrict* the term to vertebrates. - **D** is a different claim from a different part of the chapter, not this paragraph.