i watched the boy .... a bird’s nest. 1. build 2. Builds 3. to build 4. Building

slyuda1955: I watched the boy building a bird's nest.

nunny: I watched the boy .... a bird’s nest. 1. build - /Я смотрел,как этот мальчик построил гнездо.I watched the boy .... a bird’s nest. 1. build 2. Builds 3. to build 4. Building

nunny: I watched the boy .... a bird’s nest. 4. Building - Я смотрел на мальчика, делающего гнездо.
Оба варианта возможны.