hadbegun是什么時態(tài)

　　The window frames had begun to warp.

　　窗框已經開始變形。

　　He had begun to feel sleepy.

　　他已覺得困了。

　　The gold colouring had begun to rub off.

　　金黃色已經開始剝落了。

　　She had begun to be a little bored with novel writing.

　　她開始對寫小說有些厭倦了。

　　The blood had begun to cake and turn brown.

　　血開始結塊變黑。