桥拱形跨越河流。
The bridge ___arched over the river.
突然一道闪光拱形划过天空,随后传来回响的隆隆声。
Suddenly a flash ___arched across the sky, followed by an echoing rumble.
猫看到狗时拱起了背。
The cat ___arched its back when it saw the dog.