option_a.pp

class apache {
  package { 'httpd':
    ensure => present,
  }
  file { '/etc/httpd/conf/httpd.conf':
    ensure => file,
    owner  => 'root',
    group  => 'root',
    mode   => '0644',
    source => 'puppet:///modules/apache/httpd.conf',
  }
  service { 'httpd':
    ensure => running,
  }
}

option_b.pp

class ntp {
  package { 'ntp':
    ensure => present,
  }
  file { '/etc/ntp.conf':
    ensure => file,
    owner  => 'root',
    group  => 'root',
    mode   => '0644',
    source => 'puppet:///modules/ntp/ntp.conf',
  }
  service { 'ntpd':
    ensure => running,
  }
}