Before the 20th century, the measuring of the depth of the sea was
A、inaccurate
B、unknown
C、uninteresting
D、impossible
Task 1Paragraph➊Paragraph❷:Paragraph❸:Paragraph❹:A. The first step of researchB.The true nature of researchC. Combining research with educationD. Finding solutions to research questionsE. Trying not to be discouraged by failure