Directions: Read each sentence to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. The number of that part is the answer. If there is no error, the answer is (4). (ignore missing punctuations, if any)

Some witness said the grenade was thrown (1) / from a motorcycle while others said (2) / it was lobbed at the check post from a moving car (3) / No error (4).