What grenade is shaped like a baseball?

The M-67 Fragmentation Grenade is the correct answer because it is specifically designed to have a spherical shape resembling that of a baseball. This design contributes to its function, allowing for a predictable trajectory when thrown and ensuring effective dispersion of shrapnel upon detonation. The shape also aids in the ease of handling and throwing, which are crucial during combat situations.

In contrast, the M-18 Smoke Grenade typically has a cylindrical shape and is used for signaling or creating smoke screens, while the White Phosphorus Grenade also does not have the baseball shape and serves a purpose related to fire and marking targets. The Practice Grenade is designed for training purposes and is often constructed in a similar way to the actual grenades, but may not necessarily take on the same shape as the M-67. Therefore, the M-67 is uniquely identified by its baseball-like form and operational capabilities.