What does “R&D” mean?

Who is the current chief justice of the united states?

1.3.3 quiz: primary and secondary sourcesquestion 4 of 102 pointsa secondary source is reliable and credible if the person who created thesource is an expert on the topic, is educated and respected in the field ofstudy, and:

Characteristics of substistence farming include all of the following except a. the use of pesticidesb. shifting cultivation c. farmers that stay in one placed. the lack of tractors and machinery