1. Please keep off the .
2. Don't , please.
3. Please on the right.
4. litter, please.

1. grass
2. run
3. walk
4. Don't

1. 图1为禁止踩踏草坪的标志，"keep off the grass"是固定搭配，意为“请勿践踏草坪”，故填grass。
2. 图2中孩子们在奔跑，标志为禁止奔跑，"Don't run"表示“请勿奔跑”，故填run。
3. 图3为上下楼梯靠右行的标志，"walk on the right"意为“靠右行走”，故填walk。
4. 图4中女孩在扔垃圾，标志为禁止乱扔垃圾，"Don't litter"表示“请勿乱扔垃圾”，故填Don't。

I'm a robot guide dog (导盲犬). I help my owner (主人) every day. When I see this sign , I say, "Woof! Woof! 1. " If I see this sign , I tell him, "Watch out! 2. " When I see this sign , I say, "3. Let's walk there." When I see this sign near the farm, I tell him, "4. " I'm happy to help him. We are good friends.

d c b a

1. 导盲犬看到提醒不要跑的标志会叫，选项d“不要跑”符合；2. “Watch out!”提示危险，选项c“不要践踏草坪”是需要注意的；3. 说“Let's walk there”应是关于行走方向，选项b“靠右走”合适；4. 农场附近的标志，选项a“请不要乱扔垃圾”合理。