11. The __ dam is the most dangerous type of dam and has been named the "drowning machine: a large-structure b low-head high-head

## Step 1<br />The problem is asking us to identify the type of dam that is considered the most dangerous and has been referred to as the "drowning machine". The options provided are "large-structure", "low-head", and "high-head". <br /><br />## Step 2<br />The term "drowning machine" is often used to describe a "low-head" dam. This is because low-head dams can create dangerous conditions such as standing waves, hydraulic jumps, and recirculating eddies, which can trap and drown swimmers and even experienced divers.<br /><br />## Step 3<br />The term "low-head" refers to the height of the dam, which is typically less than 4 meters. This is in contrast to high-head dams, which are over 15 meters high.<br /><br />## Step 4<br />The term "large-structure" is a general term that can apply to any type of dam, regardless of its height or danger level. Therefore, it does not specifically refer to the most dangerous type of dam.