If a pink flowered snapdragon plant is crossed with a white flowered…

The correct answer is Option (4) → Pink and white flowered

In snapdragon, flower colour shows incomplete dominance: RR is red, rr is white and Rr is pink. So the pink plant is Rr and the white plant is rr.

Gametes: Rr gives R and r; rr gives only r.

Progeny: Rr (pink) and rr (white) in a 1 : 1 ratio.

Option (1) Only pink flowered — Incorrect. Half the gametes of the pink parent carry r, which gives white rr plants.

Option (2) Pink, white and red flowered — Incorrect. Red needs RR, but the white parent gives no R.

Option (3) Only white flowered — Incorrect. Half the progeny get R from the pink parent and are pink.

Option (4) Pink and white flowered — Correct. In snapdragon, flower colour shows incomplete dominance: RR is red, Rr is pink and rr is white. Crossing pink (Rr) with white (rr) gives Rr and rr in equal numbers, so the progeny are pink and white, in the ratio 1 : 1.

NCERT Extract:
Incomplete Dominance – “… The inheritance of flower colour in the dog flower (snapdragon or Antirrhinum sp.) is a good example to understand incomplete dominance. In a cross between true-breeding red-flowered (RR) and true-breeding white-flowered plants (rr), the F₁ (Rr) was pink (Figure 4.6). … What happened was that R was not completely dominant over r and this made it possible to distinguish Rr as pink from RR (red) and rr (white) .”