Answer: option 1: butyl propyl ether
Explanation:
1) Idenfify the functional group: R - O - R' => ether
2) Name the alkyl groups
a) CH3 – CH2 – CH2 – : 3 carbons => propyl
b) – CH2 – CH2 – CH2 – CH3: 4 carbons => butyl
3) rule: name the subtituents in alphabetcial order => first butyl, second propyl
4) Result: buty propyl ether.