Final answer:
The statement is true as the planet's transit in front of the star causes the largest signature in transit measurements, leading to a detectable dip in starlight, particularly useful for discovering exoplanets.
Step-by-step explanation:
The statement that the signature of a planet is largest in transit measurements when the planet and star are lined up along the line of sight to the telescope is True. A transit occurs when a planet passes directly between a star and the observer, causing a slight dimming of the star's light. This method, which has been utilized successfully by the NASA Kepler space observatory, is one of the indirect techniques used to discover exoplanets. The dip in brightness is most pronounced during the transit because it's the point at which the greatest portion of the planet's silhouette covers the star from our perspective.