Alkanes and alkenes differ in that alkene molecules contain at least one:
A. oxygen atom
B. double bond
C. triple bond
D. chlorine atom

Double bond

Explanation:

an alkene is a unsaturated hydrocarbon which means that it contain at least one double bond

The answer to your question is B. double bond.

Explanation:

Both alkanes and alkenes are hydrocarbons composed by carbon and hydrogen.

The different between these compounds is that alkanes have only single bonds are are represented as:         H    H

                                                            |     |

                                                     H - C - C - H

                                                            |      |

                                                           H    H

Alkenes have at least one double bound in their structure and are represented as

                                                   H - C = C - H

                                                          |      |

                                                          H    H

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.