RewriteEngine On in <IfModule mod_rewrite.c> every time?

I'm wondering whether I can use RewriteEngine On only once within my htaccess when it is embed in IfModule mod_rewrite.c or do I have to use it every time because it is embeded?

See example below. Thanks

<ifModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{QUERY_STRING} /?author   [NC]
RewriteRule .* - [F]
</ifModule>

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{QUERY_STRING} g=  [NC]
RewriteRule ^(.*)$ - [F,L]
</IfModule>

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>