Final answer:
Using the CSS code provided, with a default font size of 12 pixels in a browser, the paragraph's text will be sized to 18 pixels (12 pixels × 1.5em).
Step-by-step explanation:
The code snippet p { font-size: 1.5em;} sets the size of the paragraph's text in a browser, where em is a unit relative to the parent element's font size. Assuming that the default browser font size is 12 pixels, the size of the paragraph's text set by this CSS code will be:
Font-size in pixels = Default browser font size × em value
Font-size in pixels = 12 pixels × 1.5
Font-size in pixels = 18 pixels
Hence, the correct answer is c. 18 pixels.