It is the Rainbow Bridge in Norse mythology.   It spanned the air from the earth to the home of the gods.   Heimdal, the sleepless watchman god, guarded it day and night against the onrush of the Frost Giants, despite the fact that the red in the bridge's spectrum was fire. 

[解說]

1.      “It is the Rainbow Bridge in Norse mythology”：它是北歐神話中的虹橋。

2.      “It spanned the air from the earth to the home of the gods”：它跨過空中，從大地到眾神之家。 “span”：跨過，架過。

3.      “Heimdal, the sleepless watchman god, guarded it day and night”：Heimdal 這位不睡不眠的看守神，日以繼夜地守衛著它。 “watchman”：看守員、更夫。

4.      “ against the onrush of the Frost Giants”：以防霜巨人衝上來。 “onrush”：衝上、奔至。

5.      “despite the fact that the red in the bridge's spectrum was fire”：儘管事實上橋的光譜中那紅色是火。 “spectrum”：光譜。

     注意： “despite the fact that …” (儘管有 that 以下的事實)，不能省去 the fact 變成 despite that …，因為 despite 是介系詞，不能直接連上 that子句。  

[複習填充]

Bifrost is the R        Bridge in Norse mythology.  It s        the air from the earth to the home of the gods.  Heimdal, the s         watchman god, guarded it day and night         the onrush of the F        Giants, despite the        that the red in the bridge's s        was fire.

.