Conditional field group – required field*

Hi…

Thank you for your help few days back…I have come up with one more issue…

This is the mail section of my form…if you remember…

From: [your-name]

Address : [your-address]

Mobile Number : [your-number]

Email : [your-email]

City : [city]

Garden : [london][garden1][/london][delhi][garden2][/delhi][mumbai][garden3][/mumbai][newyork][garden4][/newyork][calcutta][garden5][/calcutta]

Reference Person : [your-reference]

Co-Reference Person : [your-co-reference]

HOW TO MAKE GARDEN a required field??

When I was testing, few people are not selecting anything from the field(garden) and still the form is getting submitted. I want to make that field compulsory…

Form is as follows ———-

<label> Choose City : (required)
[select* city “- Select City -” “London” “Delhi” “Mumbai” “New York” “Calcutta”]</label>

[group london]

[select* garden “- Select Garden -” “A” “B” “C” “D”]

[/group]

[group delhi]

[select* garden1 “- Select Garden -” “E” “F” “G” “H”]

[/group]

[group mumbai]

[select* garden2 “- Select Garden -” “1” “2” “3” “4”]

[/group]

[group newyork]

[select* garden3 “- Select Garden -” “5” “6” “7” “8”]

[/group]

[group calcutta]

[select* garden4 “- Select Garden -” “l” “m” “n” “o”]

[/group]