Continuity mistake: The hole in the wall Carol makes with the knife grows, depending on what angle we see it from.
Continuity mistake: Daryl and Carol are walking to an abandoned home. Carol walks by a bush with bright sunlight coming from the left of the shot. The angle changes and it's overcast with no sun. Then we see Daryl again and it's once again sunny.
Answer: Walkers are attracted to noise, they can tell who's dead and who isn't dead, in S1 when Rick and Glenn cover themselves in walkers' guts they're able to get far by walking through the herd of walkers because they smell like they're dead, but as soon as the guts get washed off by the rain the walkers immediately attack them, if you draw attention to yourself they will attack you which we've seen that many times throughout the series that it's not always successful. Whether you're covered in guts hiding under dead corpses or under a car.