A (oxygen), I believe that’s right only logical answer really in that question:)
Answer: Juan b b hi h bhg bh y bh bhu
Explanation:
Answer:
1 The computer scientists check the database for viruses
2 Nanotechnology is difficult to understand
3 The geologists study the structure and formation of the earth.
4 One is concerned with the question of whether cloning is ethica
5 In the past few years genetic researchers have made incredible strides
6 An international research team is planning a trip to Mars
Leiter
Flugzeug
Auto
Gepäck
Gehen
Laufen
First for ladder
Second for aeroplane
Third for car
Fourth for luggage
Fifth for walking
Sixth for running
Hope it helps .....