The sleepers resting directly on girder are fastened to the top flange of girder by A. hook bolts B. dog spikes C. fang bolts D. rail screws

The correct answer is: A. hook bolts

Hook bolts are a type of fastener that is used to secure sleepers to the top flange of a girder. They are made of steel and have a curved head that fits over the top of the sleeper. The bolt is then driven through the sleeper and into the girder, where it is secured with a nut.

Dog spikes are a type of fastener that is used to secure sleepers to the base of a girder. They are made of steel and have a pointed end that is driven into the ground. The spike is then bent over to secure the sleeper in place.

Fang bolts are a type of fastener that is used to secure sleepers to the base of a girder. They are made of steel and have a curved head that fits over the top of the sleeper. The bolt is then driven through the sleeper and into the ground, where it is secured with a nut.

Rail screws are a type of fastener that is used to secure rails to sleepers. They are made of steel and have a threaded shank that is driven into the sleeper. The screw is then secured with a nut.

Hook bolts are the most common type of fastener used to secure sleepers to girders. They are easy to install and provide a secure connection.