B. At-200
In beta decay the atomic number increases by 1
Density = mass/volume
D = 40/80 = 0.5g
D= 0.5g
Here are the possible answers for the following questions above:
1. H-CC-H (name) - C<span>. ethyne
</span>2. cyclic compound with both saturated and unsaturated characteristics - G<span>. benzene
</span>3. CnH2n - E<span>. general formula for alkenes
</span>4. reaction typical of unsaturated hydrocarbons - A<span>. addition
</span>5. CnH2n-2 - F<span>. general formula for alkynes
</span>6. series name of hydrocarbons with triple bond - D<span>. alkyne
</span>7. CnH2n+2 - B<span>. general formula of alkanes</span>
The answer is hard to give without any information.