Nikita shakes her head. "You'd think that would be the best solution, but it's always better to have your ace in reserve," she explains briskly. "We could run into something worse trying to get out of here, and if I can get us free without expending it--" Which hadn't been in her instructions, but seems self-evident: don't throw the grenade if you don't need to. "We're that much safer."

She doesn't want to concede, even mentally, the possibility that worse might be larger dinosaurs, but stun grenades work fine on armed pursuit, too.

"Tell me when you're ready."

Honestly, Sarah's plan would work too, but Nikita's oddly unwilling to risk killing a dozen dinosaurs if they can escape by her killing just one.