Question

Grandma is arriving ........ the 3:30 pm train.

Answer 1

$\huge\green{As-Salamu-Alykum}$


_______

For transport "by" is used .


Grandma is arriving by the 3:30 pm train .


_______


$\huge\pink{INSHALLAH it will help U}$

Answer 2

Grandma is arriving by the 3:30 pm train. When it comes to “by”, it is one of the versatile prepositions that are used in an extensive range of situations.  

You can use this preposition in different situations to let readers to understand the meaning of a sentence.  

The main purpose of using preposition is to show the link between the nouns and other words available in the sentences.