weren't the best place to study chimpanzee behavior. He dispatched a researcher named Henry Nissen to Africa. The problem was no one had invented a way to observe chimps in their natural habitat. So Nissen relied instead on techniques used by hunters to stalk game. He hid in camouflaged blinds, but the chimps spotted him and scampered off. He stationed assistants in a large circle in the dense undergrowth. Nissen's difficulties discouraged further study of wild chimps until the 1960s. The author explains that the study of chimpanzees stopped in the 1920s and did not start up until the 1960s. Which two sentences from the text show what caused this gap? A He hid in camouflaged blinds, but the chimps spotted him and scampered off. B The problem was no one had invented a way to observe chimps in their natural habitat. C He dispatched a researcher named Henry Nissen to Africa. D a He was slow and backward and spouted strange noises. E Unfortunately, these early humans were not alive for observation.

## Step 1<br />The problem is asking us to identify two sentences from the text that explain why the study of chimpanzees stopped in the 1920s and did not resume until the 1960s. <br /><br />## Step 2<br />We need to analyze each sentence and determine if it provides a reason for the gap in the study of chimpanzees.<br /><br />## Step 3<br />Sentence A talks about Nissen's unsuccessful attempts to observe chimps, but it doesn't provide a reason for the overall gap in the study.<br /><br />## Step 4<br />Sentence B directly states that there was no effective method to observe chimps in their natural habitat. This could be a reason for the study to stop.<br /><br />## Step 5<br />Sentence C talks about Nissen being dispatched to Africa, but it doesn't provide a reason for the study to stop.<br /><br />## Step 6<br />Sentence D talks about Nissen's slow and strange noises, but it doesn't provide a reason for the study to stop.<br /><br />## Step 7<br />Sentence E talks about early humans not being alive for observation, but it doesn't provide a reason for the study to stop.