Step 1: Recall the theory in question.
The idea that traits gained during an organism's life, like a giraffe stretching its neck, get passed directly to its offspring is called inheritance of acquired characters.
Step 2: Recall who proposed it.
This idea was put forward in the early 1800s by a French naturalist studying use and disuse of organs.
Step 3: Rule out the other names.
Weismann actually argued against this idea with his germplasm theory, Darwin proposed natural selection instead, and de Vries proposed mutation theory, none of them proposed acquired inheritance.
Final answer: Option 2, Lamarck.